Carnal is outside of God's will. God created sex, but with your wife.
Abraham did not sin with Hagar.
So after Abram had been living in Canaan ten years, Sarai his wife took her Egyptian slave Hagar and gave her to her husband to be his wife. (Genesis 16:3)
So Ishmael and Isaac were both sons of Abraham through different wives.
Later, we see God say this about Abraham.
I will do this because Abraham listened to me and obeyed all my requirements, commands, decrees, and instructions (Genesis 26:5)
So Abraham never acted against God's will.