Wherefore should the heathen say, {b} Where is now their God?

(b) When the wicked see that God does not always accomplish his promise as they imagined, they think there is no God.Psalm 115:2 Parallel Commentaries

Impiety of Attributing a visible Form to God. --The Setting up of Idols a Defection from the True God.
1. God is opposed to idols, that all may know he is the only fit witness to himself. He expressly forbids any attempt to represent him by a bodily shape. 2. Reasons for this prohibition from Moses, Isaiah, and Paul. The complaint of a heathen. It should put the worshipers of idols to shame. 3. Consideration of an objection taken from various passages in Moses. The Cherubim and Seraphim show that images are not fit to represent divine mysteries. The Cherubim belonged to the tutelage of the Law. 4. …
John Calvin—The Institutes of the Christian Religion

Stedfastness in the Old Paths.
"Thus saith the Lord, Stand ye in the ways, and see, and ask for the old paths, where is the good way, and walk therein, and ye shall find rest for your souls."--Jer. vi. 16. Reverence for the old paths is a chief Christian duty. We look to the future indeed with hope; yet this need not stand in the way of our dwelling on the past days of the Church with affection and deference. This is the feeling of our own Church, as continually expressed in the Prayer Book;--not to slight what has gone before, …
John Henry Newman—Parochial and Plain Sermons, Vol. VII

Psalms
The piety of the Old Testament Church is reflected with more clearness and variety in the Psalter than in any other book of the Old Testament. It constitutes the response of the Church to the divine demands of prophecy, and, in a less degree, of law; or, rather, it expresses those emotions and aspirations of the universal heart which lie deeper than any formal demand. It is the speech of the soul face to face with God. Its words are as simple and unaffected as human words can be, for it is the genius …
John Edgar McFadyen—Introduction to the Old Testament