'Only Son' in the Bible

And he said, Take now thy son, thine only son, whom thou lovest, even Isaac, and get thee into the land of Moriah. And offer him there for a burnt-offering upon one of the mountains which I will tell thee of.

And he said, Lay not thy hand upon the lad, neither do thou anything unto him. For now I know that thou fearest God, seeing thou hast not withheld thy son, thine only son, from me.

and said, By myself have I sworn, saith Jehovah, because thou hast done this thing, and hast not withheld thy son, thine only son,