John 10:30 I and my Father are one.
Jesus manifested his Father’s character
John 14:9 Jesus saith unto him, Have I been so long time with you, and yet hast thou not known me, Philip? he that hath seen me hath seen the Father; and how sayest thou then, Shew us the Father?
Matthew 11:27 All things are delivered unto me of my Father: and no man knoweth the Son, but the Father; neither knoweth any man the Father, save the Son, and he to whomsoever the Son will reveal him.
Jesus and his Father are both full of grace and truth.
John 1:14 And the word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.
Jesus and his Father are one in purpose.
Jesus’ prayer was that those who believed the gospel would be one in exactly the same way as he and his Father are one.
John 17:20 Neither pray I for these alone, but for them also which shall believe on me through their word;21 That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me. 22 And the glory which thou gavest me I have given them; that they may be one, even as we are one: 23 I in them, and thou in me, that they may be made perfect in one; and that the world may know that thou hast sent me, and hast loved them, as thou hast loved me.
The ‘oneness’ is that of character, mind (way of thinking) and purpose.
As Paul exhorts the Corinthians:
1 Corinthians 1:10 Now I beseech you, brethren, by the name of our Lord Jesus Christ, that ye all speak the same thing, and that there be no divisions among you; but that ye be perfectly joined together in the same mind and in the same judgment.
And the Philippians
Philippians 1:27 Only let your conversation (behaviour) be as it becometh the gospel of Christ: that whether I come and see you, or else be absent, I may hear of your affairs, that ye stand fast in one spirit, with one mind striving together for the faith of the gospel;
Philippians 2:2 Fulfil ye my joy, that ye be likeminded, having the same love, being of one accord, of one mind.
1 Peter 3:8 Finally, be ye all of one mind, having compassion one of another, love as brethren, be pitiful, be courteous:
Those who are born of water (baptism) must also be born of the Spirit. This means that we must change the way that we think to the way that God thinks.
So we read:
Romans 12:2 And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God.
Ephesians 4:23 And be renewed in the spirit of your mind;
When we think and behave as Jesus and his Father think and behave, we become one with them.
I hope you find this helpful.