2066. 'And I will also give you a son by her' means the Rational. This is clear from the meaning of 'a son' as truth, dealt with in 489, 491, 533, 1147. And because the whole of the rational originates in truth, 'a son' here means the rational. The Lord's first rational was represented and meant by Ishmael, born from the servant-girl Hagar. This was dealt with previously in Chapter 16. The second Rational, which is the subject here, is represented and meant by Isaac who was to be born from Sarah. The former, that represented by Ishmael, was the rational that was subsequently cast out of the house, but this latter Rational, which is represented by Isaac, is the one that remained in the house, because it was Divine. This rational is in the Lord's Divine mercy to be described in the next chapter where Isaac is the subject.