Matthew Poole and continuators on Genesis 25:1

1 THen again Abraham took a wife, and her name was Keturah.

After Sarahs death and Isaacs Marriage.

Not from any inordinate lust, which his age and eminent grace may sufficiently evince, but from a desire of more Children and of accomplishing Gods promise concerning the great multiplication of his seed.

A secondary Wife, or a Concubine, as she is called, ver. 6. and 1 Chron. 1. 32.

A distinct person from Hagar, as appears from ver. 6. and 12. and as it seems, of better quality, and younger, for Hagar was now eighty years old, and not likely to be a mother of six Children.