We have become one with Him by sharing his death. the greek word that the apostle paul uses here is ·sumphutos·. Its definition is mind blowing! It means that we are connate with Christ or born together and so sharing the same nature. Which is to say that we have been fused together with him. It speaks of a living, vital union of two individuals growing up together. The word is used of the siamese twins whose bodies were connected at one point, and whose blood flowed through two physical bodies as it does normally through one. Here the word speaks of that vital union of the believer and the Lord Jesus where God places him into Christ at the cross. This is a past and complete act, yet its results are ever abiding with us.
5 For if we have become one with Him [permanently united] in the likeness of His death, we will also certainly be [one with Him and share fully] in the likeness of His resurrection. Romans 6:5, AMP