Hebrews 2:17

Therefore he had to be made like his brothers in every respect, so that he might become a merciful and faithful high priest in the service of God, to make propitiation for the sins of the people.
(Hebrews 2:17 ESV)

Jesus became like man in every respect. This was essential. Nothing was to be left out. As such, the descendants of Abraham are his brothers. Mercy is not giving someone what they deserve. With a nature like ours, his compassion extends to us all the more because he knows and understands the trials we experience. Yet, his service (unlike ours) was always marked by faithfulness and this means we are safe. He surpasses the Jewish High Priest. "The Son of God became a man, that he might so fully enter into the feelings of the people as to be faithful, and that he might be qualified, as a high priest, to perform the great work of rendering God propitious in regard to sins." Before God, we now have favor and success.