You heard Me say, ‘I am going away, and I am coming back to you.’ If you loved Me, you would rejoice that I am going to the Father, because the Father is greater than I. — John 14:28

"My Father is greater than I". Jesus says this in the context of His voluntary humiliation—the Son submits to the Father in the economy of redemption. John 10:30 says "I and the Father are one" in essence, yet John 14:10 shows the Father dwelling in Christ and doing His works. The Father loves the Son and has given all things into His hand. The Son's willing submission isn't inferiority of nature—it's the glory of the triune God's plan of salvation.