‘And Jesus cried out and said, “He who believes in me believes not (only) in me but in him who sent me. And he who closely observes me sees him who sent me'.
This then was the essence of Jesus' proclamation. He was the One sent from God, and in Whom God could be seen. To believe in Jesus was to believe in the Father. To observe Jesus closely was to see the Father (and as John 14:7-9 evidences this meant literally). For He revealed the glory of God. And that included the fact that He and the Father are essentially One. (See John 7:16; John 8:19; John 8:42; John 10:30; John 10:38; John 13:20; John 14:7-9)