‘And Hagar bore Abram a son, and Abram called the name of his son whom Hagar bore, Ishmael. And Abram was eighty six years old when Hagar bore Ishmael to Abram.'
The end result of Sarai's planning was the birth of a son to Abram. Now his steward was no longer his direct heir for he had a son of his own. In obedience to God's words to Hagar (verse 11) he called his son Ishmael.
This birth took place when he was 86 years old. This figure is made up of 75 (Genesis 12:4) plus 10 (Genesis 16:3) plus the period to Ishmael's birth. As with all numbers in Genesis it is not necessarily to be taken literally. As we have seen both the 75 and the 10 may well be expressive of ideas rather than intended as literal numbers. Thus the 86 could well be simply a composite number resulting from these two previous numbers. Its purpose here is to bring out Ishmael's age at the birth of Isaac when compared with one hundred. (The ancients used numbers to express ideas rather than just for numerical purposes. It is questionable whether they even bothered to keep a record of age, working simply on an approximate basis. Consider how many of the ages given end either with 0, 5 or 7).