If the Israelites repented sincerely, Yahweh would be zealous to protect His chosen land from foreign invaders and have pity on His chosen people. This was His essential response. [source][source][source]
"Beginning in Joel 2:18, Israel ceases to be the object of God"s judgment and becomes instead the object of His blessing. In a similar reversal the hordes (locust and human) cease to be the instruments of God"s judgment on Israel and become instead the objects of God"s judgment. This reversal was originally foretold by God through Moses in Deuteronomy 30:1-9." [1][source]
"Between Joel 2:17-18, we should presume that the invitation and commands of Joel 2:12-17 have been accepted and obeyed." [2][source]
Context Summary
Joel 2:12-27 - The Averting Of Judgment
To rend the garment is easy, but a broken and contrite heart can be imparted only by the grace of the Holy Spirit. The love of God should bring us to repentance. He takes no pleasure in our miseries and if men repent and turn from their sin they find an immediate and loving welcome to the Father's heart and home. Joel had called for the trumpet to announce war; he now directs the trumpet blast to summon the people, from the highest to the lowest, to plead for help. Prayer and true repentance and faith bring an immediate answer. As the husband yearns over his erring but repentant wife, and is indignant with those who have maltreated her, so will Jehovah remove from us, when we turn to Him, those who have cruelly oppressed us.
The great things Jehovah did against Egypt and Babylon are an earnest of what He will do again. The earth, Joel 2:21; the lower animals, Joel 2:22; and, above all, the children of Zion, literal and spiritual, Joel 2:23, have good reason to rejoice in what awaits them. God promises not only to forgive sin, but to make us happy and well provided as if the locust and cankerworm had never settled upon our lives. [source]
Chapter Summary: Joel 2
1He shows unto Zion the terribleness of God's judgment 12He exhorts to repentance; 15prescribes a fast; 18promises a blessing thereon 21He comforts Zion with present, 28and future blessings
What do the individual words in Joel 2:18 mean?
and will be zealousYahwehfor His landand pityonHis people
Parse: Conjunctive waw, Verb, Piel, Consecutive imperfect, third person masculine singular
Root: קָנָא
Sense: to envy, be jealous, be envious, be zealous.