Hebrews 2:17
For this reason he had to be made like his brothers and sisters in every respect, so that he might become a merciful and faithful high priest in service to God, and that he might make atonement for the sins of the people — the necessity of Jesus' complete identification with humanity is grounded in his priestly function: he must be like us to represent us before God. His mercy and faithfulness are proven through suffering and obedience.