The birth of Isaac came at the end of Abraham and Sarah laying hold of God by faith despite their ups and downs. Isaac and Isaac contrast believers under the old covenant done in the strength of the flesh and those of the new covenant, that which is done supernaturally. God's tests come to see whether He is first in our life. Abraham went against human reason, counted the cost, and obeyed God in offering Isaac, the first mention of worship and also a picture of the resurrection.
