The futures of this verse with vav consec, are properly taken as perfects; nor is there any inconsistency, provided we understand, as following Joel 2:17 and preceding Joel 2:18, the fact that the priests had engaged in the penitence enjoined, and offered the supplication to which they had been summoned; neither is the omission of any express mention of the circumstance thus supposed to intervene between these verses any valid objection, especially as the grammar favours the view in question.
Then follows a manifestation of God's mercy in answer to the assumed penitence and prayer of his servants. God's jealousy and pity are both engaged—his jealousy for his land, and his compassion for his people.
His jealousy is figurative, and the allusion is probably to that of a husband who is jealous on account of any dishonour done to his wife, and who resents it more keenly than a dishonour offered to himself.
The pity is such as God ever manifests to his people when penitent; for "Like as a father pitieth his children, so the Lord pitieth them that fear him."