Philo Judaeus De Sobrietate 8

[8] Accordingly he calls Ishmael when he has now lived a space of nearly twenty years a child, speaking by a comparison with Isaac who is perfect in virtue; for, says he, "he took bread, and a skin of water, and gave it to Agar, and put it upon her shoulder, and the child also, when Abraham sent them forth from his house." ¹ And again he says, "She put the child down under a pine tree;" and further on he says, "that I may not see the death of the child." And yet before Ishmael was born and circumcised, thirteen years before the birth of Isaac, and having been now weaned for more than seven years, he was banished with his mother, because he being illegitimate was mocking the legitimate son, as though he were on terms of equality with him.