Genesis 25:16
These are the sons of Ishmael and these are their names, by their settlements, and by their encampments (sheepfolds); twelve princes (sheiks) according to their tribes.
Genesis 17:20
As for Ishmael, I have heard and listened to you; behold, I will bless him, and will make him fruitful and will greatly multiply him [through his descendants]. He will be the father of twelve princes (chieftains, sheiks), and I will make him a great nation.
Genesis 17:23
Then Abraham took Ishmael his son, and all the servants who were born in his house and all who were purchased with his money, every male among the men of Abraham’s household, and circumcised the flesh of their foreskin the very same day, as God had said to him.