"If Jesus is God, why did Paul reference both Father and Son in the Epistles?"

When we stay within the Holy Scriptures of God, we cannot err from the Truth.
When we add un-biblical terms and concepts we then err from the Truth.

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"Whosoever shall confess that Jesus is the Son of God, God dwelleth in him, and he in God." - 1 John 4:15

"If ye had known me, ye should have known my Father also: and from henceforth ye know him, and have seen him." -John 14:7

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Extracting 3 gods from 1 verse:
https://www.youtube.com/watch?v=XwzLzSyme_g

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Modalism and Trinitarianism BOTH wrong:
https://savedbypreaching.com/2019/01/modalism-oneness-and-trinitarianism-tritheist-both-wrong/