Genesis 17:25

And Ishmael his son was thirteen years old, when he was circumcised in the flesh of his foreskin.

And Ishmael his son was thirteen years old when he was circumcised in the flesh of his foreskin.. Hence the Arabians, as Josephus {w} relates, circumcise their children when at thirteen years of age, because Ishmael, the founder of their nation, was circumcised at that age; and Origen {x} asserts the same; and with which agrees what an Arabic writer says {y} of the Arabians before Mahomet, that they used to circumcise at a certain age, between the tenth and fifteenth years of their age. So Rauwolff says {z}, there are some, chiefly among the Arabians, that imitate their patriarch Ishmael. As for the Mahometans, though they circumcise, they do not always do it in the thirteenth year, as some write; for it is performed by them sometimes in the thirteenth, fourteenth, fifteenth, or sixteenth, and sometimes in the sixth or seventh year {a}. The Egyptians, according to Ambrose {b}, circumcised their children at fourteen years of age, which comes pretty near to the time of the Ishmaelites or Arabs, from whom they might receive circumcision, if not of the Israelites, as before observed. A certain traveller says {c}, the modern Egyptians, as the rest of the Mahometans, are not circumcised until the thirteenth year. The Africans circumcise on the seventh day, which comes nearer to the Jews {d}.

{w} Antiqu. l. 1. c. 12. sect. 2.
{x} Philocalia, c. 23. p. 77.
{y} Ebnol Athir apud Pocock. Specimen Arab. Hist. p. 319.
{z} Travels, part 1. ch. 7. p. 59. by Ray.
{a} Vid. Reland. de Relig. Mohammed. p. 75.
{b} De Abraham, l. 2. c. 11. p. 266.
{c} Baumgarten. Peregrin. l. 1. c. 16.
{d} Leo. African. Descriptio Africae, l. 3. p. 33.