Because that’s why the Son of Man bled on the eighth day, to prepare us for the fact that he would bleed and die for the sins of his people, and then rise again on the eighth day, beginning the new creation future.
These are the themes that Paul ties circumcision to—
‘In him you were also circumcised, with a circumcision not performed by human hands but by the circumcision of Christ, having been buried with him in baptism, in which you were also raised with him through your faith in the working of God, who raised him from the dead.’ (Colossians 2:11)
Can we see with Stephen that Abraham is not alien to all these teachings?
As Paul puts it, ‘those who have faith are children of Abraham’ (Galatians 3:7)
O Father, give us Abraham’s faith!