Paul simply states that "we" have become righteous, holy and redeemed through him, not that he became holy, just or redeemed. It still doesn't answer: why did Jesus need to be sanctified?
So, Jesus "became" sanctified so that He was our sanctification. That seems to match John 17:19 - "19 For them I sanctify myself, that they too may be truly sanctified."
No it doesn't. God says to his people "be holy because I am holy." He doesn't say "I make myself holy so that you may be holy." Only someone who is not sanctified can become sanctified. And on another occasion, Jesus asks the Father to sanctify him...yet in John 17 he sanctifies himself..etc.
The Bible is full of these little inconsistencies. I love the one where Jesus says they can't touch him because his body was not glorified yet (!). When did his body become "profane"? LOL. They were shooting in the dark, FK. And once you realize that, the magic is gone.
I don't think the Bible indicates there was a "need". Jesus said Himself:
That explains why. Christ consecrated Himself to the Father and as a consequence that holiness spread to the elect through the Spirit. See also:
God says to his people "be holy because I am holy." He doesn't say "I make myself holy so that you may be holy."
He says both, but in different contexts. The first just describes the result without explaining the "how". The second explains what makes us able to be holy. It is not a command of something we can do of ourselves, but rather an encouragement of having the right mindset in experiencing God working through you.
Only someone who is not sanctified can become sanctified.
That is only if the concept of sanctification is a one time event. The Bible says it isn't. Believers become more and more sanctified as they mature in the faith.