What about...He who knew no sin became sin for us.
Sin there is short for the longer term "sin sacrifice".
2Co_5:21 For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him.
Christ wasn't "made sin" he was made to be the
sin sacrifice or sin offering. That's what Paul means and this same thing is used in the OT, "sin" being shorthand of "sin offering".
Lev 4:29 And he shall lay his hand upon the head of the
sin offering, and slay the
sin offering in the place of the burnt offering.
H2403
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chat?t?a^'a^h chat?t?a^'th
khat-taw-aw', khat-tawth'
From H2398;
an offence (sometimes habitual sinfulness), and its penalty, occasion, sacrifice, or expiation; also (concretely) an offender: - punishment (of sin), purifying (-fication for sin), sin (-ner, offering).
Here "sin offering" is actually
just one word that means sin (similar to the single word "sin" in 2Co_5:21), but it is meant to be understood as the offering for sin
not sin itself and Paul being Jewish would know and use shorthand way of speaking of the offering for sin.
The verse should be understood as "For he hath made him to be
a sin offering for us, who knew no sin; that we might be made the righteousness of God in him."
(TLV) He made the One who knew no sin to become
a sin offering on our behalf, so that in Him we might become the righteousness of God.
(Williams) He made Him who personally knew nothing of sin
to be a sin-offering for us, so that through union with Him we might come into right standing with God.
Barnes:
2 Corinthians 5:21
For he hath made him to be sin for us - The Greek here is, ‘for him who knew no sin, he hath made sin, or
a sin-offering for us.’
Clarke:
2 Corinthians 5:21
For he hath made him to be sin for us - He made him who knew no sin, (who was innocent),
a sin-offering for us.
Matthew Henry:
He was made sin; not a sinner, but sin, that is,
a sin-offering, a sacrifice for sin.