This was AFTER Abe was circumcised.
I was baptized to wash my sins away, by faith. I received the Holy Ghost, by faith. Works of faith is obedience to the word of God. One shouldn't look for reasons not to do something, just do them by faith because the scripture says so. By doing so one will receive the blessing of God.
Jas 2:21 Was not Abraham our father justified by works, when he had offered Isaac his son upon the altar?
Jas 2:22 Seest thou how faith wrought with his works, and by works was faith made perfect?
Jas 2:23 And the scripture was fulfilled which saith, Abraham believed God, and it was imputed unto him for righteousness: and he was called the Friend of God.
Jas 2:14 What doth it profit, my brethren, though a man say he hath faith, and have not works? can faith save him?
Jas 2:17 Even so faith, if it hath not works, is dead, being alone.
Jas 2:18 Yea, a man may say, Thou hast faith, and I have works: shew me thy faith without thy works, and I will shew thee my faith by my works.
Jas 2:19 Thou believest that there is one God; thou doest well: the devils also believe, and tremble.
Jas 2:20 But wilt thou know, O vain man, that faith without works is dead?
James is a minister to the circumcision.
But Paul uses the case of Abe's faith BEFORE he was circumcised.
And the laws that came afterward CANNOT dissanul the promise made to Abe BEFORE he was circumcised.
And to make this point stand out, Abe was asleep (ie. not doing anything) while watching the LORD alone pass through the animal parts, showing it was HIS (God) faithfulness alone that would accomplish.