But indeed, we should not fail to notice from these things that are reported by the literal meaning, what generations and of what sort they are, which are propagated from Keturah.For if we remember these things, we will be able to recognize more easily those things that are said about the diverse nations in the Scriptures. For example, as when it is said that Moses took as his wife the daughter of Jethro, priest of Midian, this Midian is found to be a son of Keturah and Abraham. We know therefore that Moses’ wife is from the seed of Abraham and was not a foreigner. But also when it is written, “the queen of Kedar,” it should be known no less that also Kedar descends from the very stock of Kedar and Abraham.
So let us listen to sacred Scripture’s account to us: “Abraham was old, advanced in years. The Lord had blessed Abraham in every respect.” Why did it mention this to us? Since he was about to give good care and attention to Isaac, to the point of bringing him a bride, accordingly it mentioned to us the patriarch’s age.
[AD 253] Origen of Alexandria on Genesis 24:1