Arcana Coelestia #2079
2079. Verse 19 And God said, Truly Sarah your wife is going to bear you a son, and you will call his name Isaac. And I will establish My covenant with him as an eternal covenant, for his seed after him.
'God said' means the reply that was perceived. 'Truly Sarah your wife' means Divine Truth joined to Good. 'Is going to bear you a son' means that the Rational would come from this. 'And you will call his name Isaac' means the Divine Rational. 'And I will establish My covenant with him' means union. 'As an eternal covenant' means an eternal union. 'For his seed after him' means those who would have faith in the Lord.
Genesis 17:11
11
You shall be circumcised in the flesh of your foreskin. It will be a token of the covenant between me and you.