| Matthew Henry's Concise Commentary 2:15-27 The priests and rulers are to appoint a solemn fast. The sinner's supplication is, Spare us, good Lord. God is ready to succour his people; and he waits to be gracious. They prayed that God would spare them, and he answered them. His promises are real answers to the prayers of faith; with him saying and doing are not two things. Some understand these promises figuratively, as pointing to gospel grace, and as fulfilled in the abundant comforts treasured up for believers in the covenant of grace.
Pulpit CommentaryVerses 15-17. - "The harsh blast of the consecrated ram's horn called an assembly for an extraordinary fast. Not a soul was to be absent. Like the fiery cross, it convened old and young, men and women, mothers with infants at their breasts, the bridegroom and the bride on their bridal day. All were there stretched in front of the altar. The altar itself presented the dreariest of all sights - a hearth without its sacred fire, a table spread without its sacred feast. The priestly caste, instead of gathering as usual upon its steps and its platform, were driven, as it were, to the further space; they turned their backs to the dead altar, and lay prostrate, gazing towards the Invisible Presence within the sanctuary. Instead of the hymns and music which, since the time of David, had entered into their prayers, there was nothing heard but the passionate sobs and the loud dissonant howls such as only an Eastern hierarchy could utter. Instead of the mass of white mantles which they usually presented, they were wrapt in black goat's-hair sackcloth, twisted round them, not with the brilliant sashes of the priestly attire, but with a rough girdle of the same texture, which they never unbound night or day. What they wore of their common dress was rent asunder or cast off. With bare breasts they waved their black drapery towards the temple, and shrieked aloud, 'Spare thy people, O Lord!'" Such is Dean Stanley's vivid picture of the circumstances and scene described by the prophet in the above verses. A scene exceedingly similar occurs in the commencement of the 'OEdipus Tyrannus' of Sophocles - "Why sit ye here, my children, younger brood
Of Cadmus famed of old, in solemn state,
Your bands thus wreathed with the suppliants' boughs?
And all the city reeks with incense, And all re-echoes with your hymns and groans;
And I, my children, counting it unmeet
To hear report from others, I have come
Myself, whom all name OEdipus the Great."
Gill's Exposition of the Entire BibleBlow the trumpet in Zion,.... For the calling of the people together to religious duties, which was one use of the silver trumpets made for and blows by the priests, Numbers 10:2; sanctify a fast, call a solemn assembly; See Gill on Joel 1:14.
Jamieson-Fausset-Brown Bible Commentary15. Blow the trumpet—to convene the people (Nu 10:3). Compare Joe 1:14. The nation was guilty, and therefore there must be a national humiliation. Compare Hezekiah's proceedings before Sennacherib's invasion (2Ch 30:1-27).
Joel 2:15 Parallel Commentaries Joel 2:15 NIV
Joel 2:15 NLT
Joel 2:15 ESV
Joel 2:15 NASB
Joel 2:15 KJV Bible Hub: Online Parallel Bible | 
