'Only Son' in the Bible

And he said, "Take thy only son Isaac whom thou lovest, and get thee unto the land of Moria, and sacrifice him there for a burnt offering upon one of the mountains which I will show thee."

And he said, "Lay not thy hands upon the child, neither do anything at all unto him, for now I know that thou fearest God, in that thou hast not kept thine only son from me."

saying, "By myself have I sworn, saith the LORD, because thou hast done this thing and hast not spared thy only son,