The passage in question: 1 John 1:1-2
1That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked upon, and our hands have handled, of the Word of life;(The phrase the word of life is broken off or compounded from the single phrase to attempt to prove The word was Jesus and then of life is something else disconnected from the phrase.The next verse will not allow it.
2(For the life was manifested, and we have seen it, and bear witness, and shew unto you that *eternal life,(*Accusative feminine singular Adjective) which was with the Father, and was manifested unto us;) Eternal Life and the word of life are the same things.
The word of Life eternal life was with the Father. It is not some compound: the word .... of life. It is one phrase:" the word of life." The Oneness view contends that the preposition* with* is concerning the Life, death, burial, and resurrection of the Lord Jesus was in view as the Lamb slain from the foundation of the world and was God's intention all along for mankind's redemption.
The following is an argument from a Trinitatian and is connected with the above point.