Why was Ishmael born?
Ishmael was born because Abraham grew impatient waiting on God's promise. Since he could not see how he could father a nation without at least one son, he succumbed to the temptation to use a slave girl, and that union gave rise to the birth of Ishmael.
Les explains that God kept repeating His promises to Abraham all through his life, but some of those things took years before they were ever consummated. That long delay is exactly why the poor man grew impatient and finally succumbed to the temptation to use a slave girl. As Les puts it, after all, Abraham reasoned he could not have a nation of people if he did not have even one son. So that decision, made in impatience rather than faith, gave rise to the birth of Ishmael, which Les says would be looked at in a future program. This fits the larger seed concept Les is following out of Genesis chapter 12 and into Genesis chapter 21.