God promised Abraham a son, but Abraham did not wait on God for his son; he married a concubine and gave birth to a son—Ishmael. After he begot Ishmael, there was a thirteen-year period in which God did not speak to him (Gen. 16:16—17:1). Although he begot a son, he wasted thirteen years. This is the experience of many Christians. Whenever we act according to the flesh, God puts us aside and allows us to eat the fruit of our flesh. In God's eyes that period of time is a total waste.
After Abraham begot Ishmael, during the long period of thirteen years, there was no peace in his family. However, the Bible does not show us that Abraham had any regret. On the contrary, he treasured Ishmael very much. We can see this from his word to the Lord: "O that Ishmael might live before thee!" (17:18). Although chapter fifteen tells us that he believed, there does not seem to have been too much pursuing on his part. Day after day, he still took satisfaction in Ishmael. According to our thought, if a man has been walking according to the flesh for thirteen years and still has no feeling of guilt, there must not be much hope for him. But we must remember that Abraham was called by God. God had a purpose in him which He had to fulfill; He could not give him up. Although he backslid for thirteen years and although God did not speak to him during all that time, He was working all the time. God does not give up those whom He has chosen. If He wants to gain a person, that person cannot escape His hand. Even though Abraham had failed, God still came and looked for him. We have to realize that no fleshly pursuit, struggle, fretting, or unrest will bring us forward. We should learn to commit ourselves to the hand of the Almighty. He will lead us as He sees fit.