NOTES for Mar 2:18-22
Most Old Testament mentions of fasting tell us the following. First, it is a way to preserve purity, that is, a way to be perfected and become better. Second, and this appears much more often, people fasted in order to turn away coming misfortunes from themselves. We may recall the residents of Nineveh, who heeded the preaching of the prophet Jonah (Jonah 3:5), and Queen Esther (Esther 4:16), who asked the whole Jewish people to fast together with her. Both of these meanings bring us back to the idea that fasting was a sacrifice to God, undertaken with a view to one outcome of events or another. But most importantly, fasting, like everything else any Jew did, was meant to bring the coming of the Messiah closer.
But Christ's preaching, His death on the cross, and His Resurrection renew the words of the prophet Isaiah about the true meaning of fasting (Isa 58:6-7): mercy and love. Because only such a fast returns us to Him, makes us at least a little like Him, and restores the image of God to the human person.
Now the promise has been fulfilled and Christ has come to humanity, and every action of ours is filled with another meaning. The old wineskins of waiting for salvation burst from the wine of the new Good News: yes, salvation has come; yes, Christ is with us. For our sake, out of love for people, He endured suffering on the cross in order to redeem us from slavery to sin.
And then something altogether different is required of us Christians: to become His presence in the world, to loose the bonds of injustice, to show mercy toward others, to forget ourselves, and to live in love.