Eph 4:1 begins the second part of this epistle, in which he exhorts them to the practice of Christian virtues. (Witham)

In one hope of your vocation. The three great reasons that we have to love one another are contained in this verse, because we have but one body, of which Christ is the head. We are all animated by the same spirit, viz. the Holy Ghost, who is given to us all, and we all live in the same hope of eternal happiness. (Calmet)

Eph 4:5 contains some more reasons why Christians should love one another. We are all servants of the same God, believe the same mysteries, and receive the same sacraments, whoever may be the dispenser of them. --- One faith. As rebellion is the bane of commonwealths and kingdoms, and peace and concord the preservation of the same; so is schism, and diversity of faith or fellowship in the service of God, the calamity of the Church: and peace, unity, and uniformity, the special blessing of God therein. St. Cyprian, in his book on the unity of the Church, writeth thus: "One Church, for one is my dove. This unity of the Church, he that holdeth not, doth he think he holdeth the faith? He that withstandeth or resisteth the Church, he that resisteth Peter's chair, upon which the Church was built, doth he trust that he is in the Church?" And again, Ep. xl. "There is one God, and one Christ, and one Church, and one chair, by our Lord's voice founded upon Peter. To set up another altar, or to constitute another priesthood, besides the one altar and the one priesthood, is impossible. Whosever gathereth elsewhere scattereth. It is adulterous, it is impious, it is sacrilegious, whatsoever is instituted by man to the breach of God's disposition. Get ye far from such men: they are blind, and leaders of the blink." St. Hilary also applies this text against the Arians thus: "Perilous and miserable is it that there are now among them as many faiths as wills, and as many doctrines as manners; whilst modes of faith are written as men will, or as they will, so are understood. Whereas the one truth teaches there is but one God, one Lord, one baptism, and also one faith: hence whilst more faiths are made, they begin by falling from that which is the only faith, and end in having no faith at all." (St. Hilary, lib. ad Constantium Augustum.)

To every one of us is given grace according to the measure of the gift of Christ. That is, as it hath pleased Christ to bestow his free gifts upon us; to shew, says St. John Chrysostom, that it was not according to any merit of ours. The words also shew that Christ is the giver and author of graces, and consequently the true God. (Witham) --- We must endeavour by all means in our power to preserve this unity, especially by avoiding jealousy, or being envious of the graces which have been given to our neighour; considering that they all proceed from the same God, who divides to each one as he pleaseth. (Tirinus)

He led captivity captive.[1] St. Jerome and others expound these words of Christ's delivering the pious souls that had died before his ascension, and which were detained in a place of rest which is called Limbus Patrum [i.e. Limbo of the Fathers; sometimes called Paradise (Luke xxiii. 43.), Abraham‘ bosom (Luke xvi. 22.), or Prison (1 Peter iii. 19.)]. --- He gave gifts to men. Having delivered men from the captivity of sin, he bestowed upon them his gifts and graces. (Witham) --- Wherefore he, David, in Psalm lxviii. makes use of these words, in order to shew that these gifts were gratuitous, and that no person had a right to complain that another had received more: after this the apostle proceeds to shew that Christ even descended to the lower parts of the earth, in order to teach us humility; whence he concludes that we ought to be humble and live in union with our brethren, which is the chief subject of the present chapter. (Tirinus)

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Captivam duxit captivitatem. On which words St. Jerome: (p. 364.) Descendit ad inferna, et sanctas animas, quæ ibi detinebantur, secum ad cœlos victor deduxit. See 1 Peter chap. iii.

Into the lower parts of the earth. This cannot signify into the grave only, especially since in that which we look upon as the apostles' creed, we first profess to believe that he was buried, and afterwards that he descended into hell. (Witham)

Some indeed he gave to be apostles, &c. It is said (1 Corinthians xii. 28.) that God (even with the Greek article) gave some to be apostles, &c. and here it is said of Christ: another proof that Christ is the true God. (Witham)

Unto a perfect man, unto the measure of the age [2] of the fulness of Christ; that is, according to the measure of the full and perfect age of Christ. Of the ancient interpreters, some expound this of what shall happen in the next world, after the resurrection, when all the elect shall have bodies every way perfect; and as some conjecture, (when all who rise by a happy resurrection) shall seem to be about thirty, of the stature and age of Christ when he suffered. But others, especially the Greek interpreters, understand this verse of a spiritual perfection in this life, by which the members of Christ's mystical body meet in the unity of faith, and increase in grace and virtue by imitating Christ, and following his doctrine and example. And this seems more agreeable to what follows: that we may not now be children, tossed to and fro by the wickedness,[3] of men. The Greek word, as St. Jerome observes, may signify by the deceit or fallacy of men; by illusion, says St. Augustine. And St. John Chrysostom tells us it is spoken by a metaphor, taken from those who cheat at dice, to gain all to themselves, to draw men into errors and heresies. Such, about that time, were the disciples of Simon the magician. (Witham) --- Every one must labour to become perfect in the state in which he is placed, by increasing in the knowledge and love of God, which knowledge and love of God constitute the full measure of a Christian. (St. John Chrysostom) --- St. Augustine also admits to another interpretation of this place, but prefers the former. According to him, it may mean: that all people, at the resurrection, will be raised in such a state as they would have had if they lived to the age of Christ, viz. thirty-three years. (St. Thomas Aquinas) --- This text of the apostle, assuring to the one true Church a perpetual and visible succession of pastors, in the ministry, successors of the apostles, warranted the holy Fathers in the early ages of the Church, as it does Catholics of the present day, to try all seceders by the most famous succession of the popes or bishops of Rome. See this in St. Irenæus, lib. iii. chap. 3; Tertullian, in præscript. Optatus. lib. ii. contr. Parmen.; St. Augustine, cont. ep. Manic. chap. iv., Ep. 165 & alibi.; St. Epiphanius, hæres. 27.

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In mensuram ætatis plenitudinis Christi; Greek: eis metron elikias (ætatis vel staturæ) Greek: tou pleromatos tou Christou. See St. Augustine, lib. xxii. de Civ. Dei, chap. xv. et seq. tom. vii. p. 678.; St. Jerome in Epitaphio Paulæ. tom. iv. part 2. p. 635.; St. John Chrysostom, hom. xi.

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In nequitia hominum, Greek: en te kubeia, in fallacia: Greek: kubeia, est lusus aleæ. See St. John Chrysostom, p. 821. Ed. Sav.

by what every joint supplieth, &c. St. Paul compares the Church and mystical body of Christ (as he does elsewhere) to a natural body, whose perfection depends on the harmony, union, and concurrence of all the different parts; and so in the Church, of which Christ is the head, some are apostles, some prophets, &c. and Christ hath been pleased to give them different offices, talents, and gifts, for the edifying and increase of the whole body, which is his Church, that they may no longer be like Gentiles,...alienated from the life of God; from such a life as God requires they should lead. (Witham) --- The obscurity of this verse my be thus explained: the apostle compares the mystical body of the Church, of which Christ is the head, to the natural body of man; and as the head directs different members to different operations, according to their various properties, so in the Church Christ distributes to each his proper office, that being all intent upon their relative duties, all may grow up in charity and become perfect. (Estius)

Who despairing,[4] (without faith and charity) according to the Latin text and some Greek manuscripts; though according to the ordinary Greek, without grief or sorrow, (to wit, for their sins) have given themselves over to all manner of vices, unto covetousness.[5] Some take notice that the Greek word may not only signify avarice, or covetousness of money, but any unsatiable desires or lusts. See Chap. v. ver. 3. and 5. (Witham)

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Deperantes. The Latin interpreter seems to have read Greek: apelpikotes, as in some manuscripts, but in most other copies Greek: apelgekotes, indolentes. See St. Jerome in his Commentary, p. 368.

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In avaritiam: Greek: en pleonexia, in cupiditate. See ver. 3. of the next chapter.

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Be angry, and sin not, as it is said Psalm iv. 5. Anger, as a passion of the mind, may proceed from a good motive and be guided by reason; as our Saviour, Christ, (Mark iii. 5.) is said to have looked about at the Jews with anger, i.e. with a zeal against their blindness and malice. --- Let not the sun go down upon your anger. If moved to anger, return without delay to a calmness of mind and temper. (Witham) --- Be angry when reason or necessity compels you; but even then, so restrain your anger that you neither offend God nor scandalize your neighbour. Moreover, lay it aside as soon as you are able, so that the sun go not down upon your anger. (Jansenius)

That it may afford grace to the hearers; i.e. that your speech may contribute to their good and edification. (Witham)

Grieve not the Holy Spirit: not that the Holy Ghost can be contristated. It is a metaphor; and the sense is, sin not against the Holy Ghost. (Witham) --- To contristate the Holy Spirit is a metaphorical expression, which signifies to offend God, or the Holy Ghost, who has sealed us by the sacraments of baptism and confirmation with particular marks, by which we shall be distinguished from others in the day of our retribution. (Sts. Chrysostom, Jerome, Ambrose, &c.)