'Eldest' in the Bible

And Abraham said to his servant, the eldest of his house, who ruled over all that he had, Put thy hand, I pray thee, under my thigh,

And he searched carefully: he began at the eldest, and ended at the youngest; and the cup was found in Benjamin's sack.

And the sons of Reuben, Israel's eldest son, their generations, after their families, according to their fathers' houses, by the number of the names, according to their polls, every male from twenty years old and upward, all that went forth to military service:

And the three eldest of the sons of Jesse had gone and followed Saul to the battle; and the names of his three sons that went to the battle were Eliab the firstborn, and the second to him Abinadab, and the third Shammah.

And David was the youngest; and the three eldest had followed Saul.

And Eliab, his eldest brother, heard while he spoke to the men; and Eliab's anger was kindled against David, and he said, Why art thou come down? and with whom hast thou left those few sheep in the wilderness? I know thy pride and the naughtiness of thy heart; for thou art come down that thou mightest see the battle.

And Saul said to David, Behold my eldest daughter Merab, her will I give thee to wife; only be thou valiant for me, and fight Jehovah's battles. But Saul thought, My hand shall not be upon him, but the hand of the Philistines shall be upon him.

And he took his eldest son, that should have reigned in his stead, and offered him up for a burnt-offering upon the wall. And there was great wrath against Israel; and they departed from him, and returned to their own land.