John Chrysostom
What Paul teaches others when he says, "With thanksgiving let your requests be made known to God" (Phil 4:6), he also does himself. He instructs us to begin everything with these words and to thank God before all else.
Nothing is so pleasing to God as thanksgiving, both for oneself and for others. Therefore Paul begins almost every epistle in this way. Here, however, it was more necessary to do this than in the others.
One who gives thanks gives thanks as one who senses a benefit and, as it were, gives back for the grace bestowed. But grace is neither a debt, nor a reward, nor a repayment.
Everyone needs to know this, and the Corinthians especially needed it, since they were inclining toward those who divided the Church.
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"My God." Because of his great love, he makes his own what belongs to all. He calls God his own, as the prophets also were accustomed to say: "O God, my God." At the same time he instructs them also to say the same.
The one who speaks thus leaves behind everything human and turns to Him Whom he calls upon with great love. Such speech belongs to one who is constantly turning from earthly things to God, prefers Him to all things, and gives Him continual thanks.
He not only thanks Him without ceasing for grace already given, but also offers Him praise for every good thing he receives.
Therefore he did not simply say, "I thank," but, "continually for you." He teaches them to give thanks always, and not to anyone else, but only to God.
"Because of the grace of God." Do you see how he corrects them everywhere? Where grace is, there are no works. Where works are, there is no grace. Therefore, if grace has been given to you, why are you high-minded? Why are you puffed up?
"Given to you." And through whom was it given? Through me, or through another apostle? No, but through Jesus Christ. This is what the expression "in Christ Jesus" means.
Notice that he often uses "in" (en) instead of "through" (dia). Therefore it means the same thing as "through."