What does the New Testament teach about the Holy Trinity being of one essence?

At the Archangel Gabriel’s Annunciation to St. Mary, he said to her, “The Holy Spirit will come upon you, and the power of the Highest will overshadow you; therefore, also, that Holy One who is to be born will be called the Son of God” (Luke 1:35).

At the baptism of Christ, the Holy Trinity was clearly revealed. He who was baptized was the beloved Son in whom the Father is well pleased; the Father testified of Him from heaven; and the Holy Spirit descended upon Him like a dove (Matt. 3:16–17; Mark 1:9–11; Luke 3:22).

At the transfiguration of Christ on Mount Tabor before the disciples Peter, James, and John, the Holy Spirit appeared as a bright cloud; and the Father testified: “This is My beloved Son, in whom I am well pleased. Hear Him!” (Matt. 17:5).

In His parting prayer, the Lord Christ spoke of the Holy Spirit as another Helper, whom He would send from the Father (John 14:16–17, 26).

In the last commandment that the Lord Christ gave to His disciples before the Ascension, He proclaimed to them the oneness of the essence of God, commanding them to baptize believers in the name (not in the names) of the Father, the Son, and the Holy Spirit (Matt. 28:19–20).

The three Hypostases have equal knowledge because they are one essence.

The first ecumenical council in Nicaea in 325 A.D. resolved, after inquiring into the Holy Bible and the tradition the Church, that Jesus Christ is “the only-begotten Son of God, begotten of the Father before all ages. Light of Light, true God of true God; begotten not created; of one essence with the Father” (the Creed of Faith).