A fruitful one signifies spiritual good from charity.

(References: Apocalypse Explained 357)

3234. THE INTERNAL SENSE

Verse 1 And Abraham took another wife; and her name was Keturah.

'Abraham took another wife' means a further state which the Lord, whom Abraham represents, passed through - for 'Abraham and Sarah' represented the Lord as regards the Divine Celestial, 'Abraham and Keturah' the Lord as regards the Divine Spiritual, so that 'Abraham' here represents the Lord as regards Divine Spiritual Good, and his wife as regards Divine Truth allied to that Good. 'And her name was Keturah' means the essence of this Divine Truth.