John 14:28
You heard me say, ‘I am going away and I am coming back to you.’ If you loved me, you would be glad that I am going to the Father, for the Father is greater than I.
If in the Trinity the divine persons are equal, why does Jesus say that the Father is superior to him?
Jesus makes that statement in reference to his human nature. When the fullness of time came, the second divine person of the Trinity, the Son (Logos), hypostatically uniting to himself a flesh animated by a rational soul, became man (John 1:14; Galatians 4:4). When, after the resurrection, he had to go to the Father, the Son had to take with him the human nature that had become his own. As a divine person, in fact, Jesus was already with the Father, being with him one God (John 10:30; 16:15), not limited to one place (1 Kings 8:27; Psalms 139:5-12; Proverbs 15:3; Jeremiah 23:24; Mark 10:27). Then with that: “I go and I will return”, and: “I go to the Father”, we must understand the human nature of Jesus. And it is according to human nature that Jesus is inferior to his Father. While as a divine person (John 1:1-3.14; 20:28; Acts 20:28; Romans 8:9; Colossians 1:16-17; 2:9; Titus 2:13; 1 Peter 1:10-11; 2 Peter 1:1; Revelation 1:17-18; 22:6.16) Jesus is equal to the Father (John 16:15) and is one with him (John 10:30). The Son is not the Father, but participates fully in the same and indivisible nature of the Father, and therefore is one God with him (and with the Holy Spirit).
Cristiani Cattolici Romani 