"We ourselves are eye-witnesses able and willing to testify to the fact that the Father did send the Son to save the world. Everyone who acknowledges that Jesus is the Son of God lives in him, and he lives in God. So we have come to know and trust the love God has for us. God is love, and the man whose life is lived in love does, in fact, live in God, and God does, in fact, live in him. So our love for him grows more and more, filling us with complete confidence for the day when he shall judge all men—for we realize that our life in this world is actually his life lived in us." (1 John 4:14-17)
* * *
"The closer any creature draws to God, the more it shares in His goodness and the more abundantly it is filled with gifts infused by Him. Thus he who comes closer to a fire shares to a greater extent in its heat. But there can be no way, nor can any be imagined, by which a creature more closely adheres to God than by being united to Him in unity of person. Therefore, in consequence of the very union of His human nature with God in unity of person, Christ’s soul was filled with habitual gifts of grace beyond all other souls. And so habitual grace in Christ is not a disposition for union, but is rather an effect of union."
Thomas Aquinas, Summa Theologica