And after that came his brother out, and his hand took hold on Esau's heel; and his name was called Jacob: and Isaac was three score years old when she bore them.
Read Chapter 25
Gregory of Nyssa
There was the example of the patriarch Isaac, who did not marry at the peak of his youth, in order that marriage should not be a deed of passion; because of the blessing of God upon his seed. He continued in the marriage until the birth of his twin sons, and later, closing his eyes, he entered again fully the realm of the unseen. This is what the story of the patriarch seems to mean, in my opinion, when it refers to the failing of his sight.