This is from Cornelius a Lapide’s commentary on 1 Cor 15:10:
" Yet not I, but the grace of God which was with me. It plainly appears from this passage against Luther and Calvin that man has free-will, and that God alone does not work everything in us, but that our free-will co-operates with Him, even in supernatural works, for the Apostle says with me , not in me , and I laboured more abundantly than they all.
Again, the verb to be supplied in this passage is properly laboured. Then it will run. “Yet it was not I that laboured, but the grace of God, which laboured with me.” S. Paul does not here exclude the co-operation of the will, but only attributes the praise due to the work to grace as its more worthy cause. But the sense will be the same if you read with the Greek Fathers and S. Jerome, “was with me.” The meaning then is, “which was with me to help me.” I laboured much of my own free endeavour, yet I did not so labour as to give myself all the praise and glory of my labour; but it was the grace of God which aroused me, aided me, strengthened me for this labour; to it, therefore, I give the first and best praise of my labour.”
S. Bernard (“On Grace and Free-will,” sub finem ) says. “ ‘It was not I, but the grace of God with me’ implies that he was not only a minister of the work by producing it, but in some way a companion of the worker by consenting to it. Elsewhere S. Paul says of himself, ‘We are workers together with God’ (1 Cor. iii. 9); hence we make bold to say that we merit to receive the kingdom because we are joined to the Divine Will by the voluntary surrender of our own will .”
See also Anselm, Chrysostom, Theodoret ( in loco ); also Jerome ( contra Pelag. lib. ii.), Gregory ( Morals , xvi. c. 10), S. Augustine ( de Liber. Arbit. c. 17, and Serm. 13 de Verbis Apost .). He says there: “ If you were not a worker, God could not be a co-worker ."