Joel indicates that the first thing is that they start using God’s gifts (again) to serve him. When the famine disappears and the land yields fruit again, they will first restore the sacrificial service. Joel 1 had indicated how the plague of locusts stopped the sacrificial worship (Joel 1:6, Joel 1:13). Personal hunger is terrible, but the fact that the service to God had stopped is the worst tragedy. Christ will say, seek first God’s kingdom, and then the rest of what you need will be provided (Matthew 6:33). This requires a reversal of our hearts. As humans, we are selfish. God takes us by the hand: serve me first, and only then everything will turn out well for you.
13 Déchirez vos cœurs et non vos vêtements, Et revenez à l'Eternel, votre Dieu; Car il est compatissant et miséricordieux, Lent à la colère et riche en bonté, Et il se repent des maux qu'il envoie.