Watchman Nee Levi, at the time of the battle of the kings, was not yet even thought of. Yet he was "in the loins of his father" Abraham, and, "so to say, through Abraham", he offered (Hebrews 7.9, 10).
Now this is the exact meaning of 'in Christ'. Abraham, as the head of the family of faith, includes the whole family in himself. When he offered to Melchizedek, the whole family offered in him to Melchizedek. They did not offer separately as individuals, but they were in him, and therefore in making his offering he included with himself all his seed.
So we are presented with a new possibility. In Adam all was lost. Through the disobedience of one man we were all constituted sinners. By him sin entered and death through sin, and throughout the race sin has reigned unto death from that day on. But now a ray of light is cast upon the scene. Through the obedience of Another we may be constituted righteous.