Today's Gospel is that awe-ful parable of the last judgment, when "the King" will say to the "sheep", "Come! When I was hungry, you gave me food; when I was thirsty you gave me drink..." And to the "goats", "Away from me: you did not give me food, or drink, or clothes, or a visit..." Because "whatever you do for the least of my brothers, you do (or fail to do) for me."
This would seem to put all the onus for charity on us, as if the initiative had to come from us, the strength had to be ours, the goodness of heart all ours. But St. John tell us "It is not that we have loved God, but that God first loved us." So that our part is not an initiative, but a response. The real "obligation" we have, then, is to pay attention to what God is doing, so that we can respond.