The Hebrew word rendered Behold calls attention to what follows.

I made him a witness to the peoples: The Hebrew verb rendered made (literally “gave”) means “appointed” here. The pronoun him refers back to David. David was probably a witness to the peoples since his victories over the surrounding nations showed God’s power at work through him (see Psa 18.43-50). The peoples refers to the nations surrounding Israel. For this whole line Good News Translation has “through him I showed them [the nations] my power.”

A leader and commander for the peoples spells out two other responsibilities that David had. The Hebrew word for leader refers to a ruler or prince. This term occurs in 2 Sam 7.8, where God calls David a “prince over my people Israel.” As both a political and military commander, David issued orders. The peoples refers to the same foreign nations mentioned in the previous line. For the peoples probably means “in the presence of the nations.” The surrounding nations recognized David’s leadership over Israel. This phrase may mean “over the nations” if there is poetic exaggeration here. Then the whole line means David ruled the nations.

For the translation of this verse consider the following examples:

• See, I appointed him to bear witness to my power,
and to be a leader and commander in the eyes of nations [or, before nations].

• See, through him I showed my power to the nations,
and he was a leader and commander of the peoples.

Quoted with permission from Ogden, Graham S. and Sterk, Jan. A Handbook on Isaiah. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here .