Who anointed both Saul and David to be king?

The correct answer is Samuel because he is the prophet specifically chosen by God to perform the anointing of both Saul and David as kings over Israel. In the biblical narrative, Samuel first anoints Saul when God instructs him to do so, marking the beginning of Israel's monarchy. Subsequently, after God's rejection of Saul due to his disobedience, Samuel is also the one who anoints David, signifying God's choice for the next king. This act of anointing is crucial as it symbolizes divine selection and approval for leadership in Israel.

The other options are figures from the Old Testament but do not play the role of anointer in this specific context. Eli was a priest and judge but did not anoint either king. Nathan was a prophet during David's reign, known for his later interactions with David, particularly in relation to David’s sin. Gad, another prophet, also served during David's time but was not involved in the anointing of either Saul or David. Thus, Samuel's unique role in anointing both kings distinctly identifies him as the correct answer.