Abraham was righteous because of faith not circumcision. "Circumcision is that of the heart, in the Spirit, not in the letter" (from Romans 2:29).
Christ fulfilled and cancelled the legal requirements that were against us because of His perfect life and sacrifice. "He forgave us all our sins, having canceled the charge of our legal indebtedness, which stood against us and condemned us; he has taken it away, nailing it to the cross."(from Colossians 2:13-14)
We shouldn't judge someone who does or doesn't observe the Sabbath. "Who are you to judge someone else’s servant? To their own master, servants stand or fall. And they will stand, for the Lord is able to make them stand. One person considers one day more sacred than another; another considers every day alike. Each of them should be fully convinced in their own mind. Whoever regards one day as special does so to the Lord. Whoever eats meat does so to the Lord, for they give thanks to God; and whoever abstains does so to the Lord and gives thanks to God." (Romans 14:4-6)
Similarly, Colossians 2:11-23 is about being free in Christ, free from "legalism" and the false humility of rules, regulations and laws that overshadow what Christ's done.