Fill up and complete my joy by living in harmony and being of the same mind and one in purpose, having the same love, being in full accord and of one harmonious mind and intention. Philippians 2:2(AMPC)
Oneness is integrity and wholeness.
God is One, there’s only One God yet we understand from Scripture that there are three persons in the Godhead that’s Father, Son, and Holy Spirit. There’s no contradiction here when we understand that being one in this sense means harmony.
The three distinct persons in the Godhead are in perfect harmony. They are the same in nature and character. They are one in thought, intent and purpose. That’s what makes God Righteous and Holy.
Likewise all of us believers, as the one Body of Christ we ought to think, live, and walk in harmony. We should be one in thought, intent and purpose especially towards one another. We can only attain this by yielding to the mind of Christ. When we see everyone as God sees each and every one of us – valued and esteemed then that’s how we will treat everyone. Then we will live in harmony just like Father Son and Holy Spirit in the Godhead. Then we will live upright and whole.