The Birth of Isaac (Genesis 21)
Finally, after 25 years, God fulfilled His promise to provide a son and heir to Abraham and Sarah! The wait had been difficult, sometimes dispiriting, sometimes frustrating. But, true to His word, God did just as He promisedand just when He promised the previous year (18:10, 14).
But the birth of the promised son did not lead to peace and joy. Instead, the fruit of Abraham and Sarah's attempt to fulfill God's promise through Hagar was now beginning to be borne. Strife rent the household of Abraham, with Sarah seeking to ensure Isaac's preeminence and resenting Abraham's love for Ishmael, his other son. Although the narrative presents the entire transaction in a relatively brief space, it is likely that the tensions in the household had been building for quite some time. Ishmael's ill treatment of Isaac was merely the straw that broke the camel's back.
Abraham was distressed by the entire affair. He truly loved Ishmael (17:18) and, given God's pointed mention of Hagar in 21:12, Abraham may have had tender feelings toward her. He probably tried everything he could to keep peace in the house. But it was to no avail. In this circumstance, God told Abraham to heed the words of Sarah. Whether or not Sarah had a right to feel and behave as she did, God's plan necessitated the separation of Ishmael from the household.
In requiring the separation, however, God reassured Abraham that Ishmael would be blessed, "because he is your seed" (verse 13). In other words, although God had not obligated Himself to provide for Ishmael, nor bless him, God would graciously bless Ishmael because God loved Abraham and Abraham loved Ishmael. God's grace sometimes falls on others because of His love toward His people. When we become His children, God's love and affection is extended to more than simply ourselves. Because He loves us and we love others, God, for our sake, sometimes extends His protection and blessing to those we love. This is born out explicitly in 1 Corinthians 7:14, where Paul tells us that an unbelieving spouse is sanctified by the believeran extension of God's love toward us. So, though we are separated from the world by the plan and call of God, nevertheless we are given the sure knowledge that because of our separation to God, our unconverted loved ones will often share in the overflow of God's grace.
We should also stress in this context the kinds of problems that can arise whenever we depart from God's pattern for marriagethat a man and woman unite for life in a loving monogamous relationship (Matthew 19:5-6). As we see from the example of Abraham, Sarah and Hagarhere in Genesis 21 and earlier in chapter 16relationships contrary to this pattern lead to heartache, jealousy, bitterness and misery. We see many of the same problems again when we come to the life of Abraham's grandson Jacob. These stark examples should remind us of the kinds of consequences we saddle ourselves and others with when we decide to ignore God's laws and instructions.