76 If we seek to delve more deeply into the mysterious working of the Spirit, we learn that he groans within us, saying “Abba!” Indeed, “the proof that you are children is that God has sent the Spirit of his Son into our hearts, crying, ‘Abba! Father!’” ( Gal 4:6). For “the Spirit bears witness with our spirit that we are children of God” ( Rom 8:16). The Holy Spirit at work in Christ’s human heart draws him unceasingly to the Father. When the Spirit unites us to the sentiments of Christ through grace, he makes us sharers in the Son’s relationship to the Father, whereby we receive “a spirit of adoption through which we cry out, ‘Abba! Father!’” ( Rom 8:15).
Source: Dilexit Nos (Vatican.va)