Arcana Coelestia #3243
3243. 'All these were the sons of Keturah' means as regards matters of doctrine and the worship that sprang from these. This is clear from the meaning of 'sons' as truths and matters of doctrine, dealt with in 489, 491, 533, 1147, 2623, and from the representation of 'Keturah' as Divine Spiritual Truth joined to Divine Spiritual Good, dealt with in 3236, 3237; thus things which belong to the Lord's spiritual kingdom are meant. And because the worship of that kingdom is in accordance with matters of doctrine, therefore the sons of Keturah mean matters of doctrine, and also the worship that sprang from these.
Arcana Coelestia #2623
2623. 'A son' means the Divine Rational. This is clear from the meaning of 'a son'. In the internal sense of the Word 'a son' means truth, 489, 491, 533; and because truth is the principal element in the rational, 2072, 2189, 'a son' also means the rational. But here the Divine Rational is meant in which the principal element is good. 'Isaac' too, to whom 'a son' refers, represents this good, as will be shown further on.