All was not well in Abraham"s household even though God had provided the heir. Ishmael was a potential rival to Isaac"s inheritance. This section records another crisis in the story of Abraham"s heir. Waltke pointed out six parallels between Hagar and Ishmael"s trek and Abraham and Isaac"s (ch22). [1][source]
Normally in ancient Near Eastern culture the son of a concubine became the heir of his mother but not of his father (cf. Judges 9:1-3). Now that Abraham had a son by his wife, Sarah did not want Ishmael to share Isaac"s inheritance. Weaning would have normally occurred at age two or three (cf. 1 Samuel 1:22-24; Hosea 1:8). The Hebrew word translated "mocking" ( Genesis 21:9) comes from the same root as Isaac"s name and means "laughing." However this participle is in the intensive form in Hebrew indicating that Ishmael was not simply laughing but ridiculing Isaac (cf. Galatians 4:29). Ishmael disdained Isaac as Hagar had despised Sarai ( Genesis 16:4). Abraham understandably felt distressed by this situation since he loved Ishmael as well as Isaac (cf. Genesis 17:18). God appeared to him again (the seventh revelation) to assure Abraham that Sarah"s desire was in harmony with His will (cf. Genesis 17:19-21). He encouraged Abraham to divorce Hagar. [source][source][source]
"But how could God ask Abraham to do evil if divorce is always a sin? The answer must be that divorce in this case is either not a sin or else is the lesser of two evils." [2][source]
For other instances where God apparently commanded divorce, see Deuteronomy 21:10-14 and Ezra 9-10. Since God makes the rules, He can also alter them according to His sovereign will. [source][source][source]
"The key to Sarah"s demand lies in a clause in the laws of Lipit-Ishtar where it is stipulated that the father may grant freedom to the slave woman and the children she has borne him, in which case they forfeit their share of the paternal property." [3][source]
The laws of Lipit-Ishtar were laws that governed life in Mesopotamia that antedated the Mosaic Law. [source][source][source]
The focus of this revelation is a clarification of God"s purposes for each of the two sons. God would bless Abraham through Ishmael as well as through Isaac. [source][source][source]
"As Cain suffered both banishment from the divine and protection by the divine, so Ishmael is both loser and winner, cut off from what should be his but promised a significant lineage." [4][source]
The concluding description of Ishmael"s experiences ( Genesis 21:14-21) provides information essential to understanding and appreciating later references to him and his descendants in the text. Ishmael became the father of12sons ( Genesis 25:13-16) as Jacob did. From his sons came the Arab nations that have ever since been the chief antagonists of the Israelites. The term "Arab" (someone from Arabia) came into use for the first time in the ninth century B.C. [5] Hagar chose a wife for her son from her homeland, Egypt. [source][source][source]
"In this respect she does not display the wisdom used by Abraham in choosing, as he did, a god-fearing wife for his son." [6][source]
"The picture of Ishmael as the rejected son is complete: he is the son of a slave woman, married to an Egyptian, lives outside normal social bounds, and is remembered for his hostilities." [7][source]
God not only makes promises but also provision. His provision of what He has promised results in great joy and should lead to separation from whatever might hinder His program of blessing. See Paul"s use of this account in Galatians 4:21-31. [source][source][source]