The Catechism in Questions & Answers

105. What passages in Holy Scripture attest that Jesus Christ is also always true God?

It was only as true God that Jesus Christ was able to say: “I and My Father are one” (John 10: 30), and thereby express that He is identical in essence with the Father.
At Jesus’ baptism in the Jordan, a voice from heaven was heard saying: “This is My beloved Son, in whom I am well pleased” (Matthew 3: 17). During His transfiguration, the Father likewise emphasised that Jesus is the Son of God: “This is My beloved Son, in whom I am well pleased. Hear Him!” (Matthew 17: 5). The words of Jesus: “He who has seen Me has seen the Father” (John 14: 9) also attest that He is God.