To be fruitful relates to goodnesses, and to be multiplied, truths.

(References: Arcana Coelestia 1014, 1018)

2834. 'And offered it as a burnt offering instead of his son' means their sanctification and adoption. This is clear from the meaning of 'offering as a burnt offering' as being sanctified, dealt with in 2776, and from the meaning of 'instead of his son' as being adopted, that is to say, by the Lord's Divine Human, meant here by 'Abraham', 2833. The adoption of those who were spiritual is described in John,

Jesus said, I am the vine, you are the branches. He who abides in Me, and I in him, he it is that bears much fruit, for without Me you can do nothing. John 15:5.

'The vine' is the spiritual Church, see 1069.