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.
16. sanctify the congregation—namely, by expiatory rites and purification with water [Calvin], (Ex 19:10, 22). Maurer translates, "appoint a solemn assembly," which would be a tautological repetition of Joe 2:15.
elders … children—No age was to be excepted (2Ch 20:13).
bridegroom—ordinarily exempted from public duties (De 24:5; compare 1Co 7:5, 29).
closet—or, nuptial bed, from a Hebrew root "to cover," referring to the canopy over it.