When all the people were baptized, it came to pass that Jesus also was baptized; and while He prayed, the heaven was opened. 22 And the Holy Spirit descended in bodily form like a dove upon Him, and a voice came from heaven which said, “You are My beloved Son; in You I am well pleased.” (Lk 3:21-22)
This verse is an indication that there are three persons in the deity—called the Triune God (or the Trinity). Triune simply means “three in one.” This is certainly a theological mystery and something that is beyond our human comprehension. The three persons of the Godhead are eternal, and have always existed together in loving unity. This is one of several mysteries of faith that followers of Jesus are not able to comprehend now, but will understand fully in eternity.
When Jesus was baptized, the three persons of the Godhead were present. The Father spoke from Heaven; the Son fulfilled all righteousness in being baptized; and the Spirit descended upon Jesus as a dove. (Mt 3:16-17)
There are diversities of gifts, but the same Spirit. 5 There are differences of ministries, but the same Lord. 6 And there are diversities of activities, but it is the same God who works all in all. (1 Cor 12:4-6) This verse above speaks about: 1) the Spirit, 2) the Lord [Jesus]; and 3) God [the Father].
. . . and declared to be the Son of God with power according to the Spirit of holiness, by the resurrection from the dead. (Rom 1:4) This verse confirms that Jesus was the Son of God [the Father], who was raised from the dead by the power of the Holy Spirit. (see Rom 8:11) So this is another indication of a Triune God.
Another verse that speaks to our topic is:
. . . remembering without ceasing your work of faith, labor of love, and patience of hope in our Lord Jesus Christ in the sight of our God and Father, 4 knowing, beloved brethren, your election by God. 5 For our gospel did not come to you in word only, but also in power, and in the Holy Spirit and in much assurance, as you know what kind of men we were among you for your sake. (1 Thes 1:3-5)
We are people of faith, and the doctrine of the Trinity is a matter of faith. It was confirmed as official church doctrine in AD325 at the Council of Nicea. As is true of so many facets of our faith, we know that one day the Lord will open our eyes to all truth when we are with Him, face to face. God bless you.