C. F. Keil and Franz Delitzsch on 1 Kings 3:9

1Ki 3:9 ונתתּ, therefore give. The prayer (commencing with ועתּה in 1Ki 3:7) is appended in the form of an apodosis to the circumstantial clauses וגו ואנכי and וגו ועבדּך, which contain the grounds of the petition. שׁמע לב, a hearing heart, i.e., a heart giving heed to the law and right of God, “to judge Thy people, (namely) to distinguish between good and evil (i.e., right and wrong).” “For who could judge this Thy numerous people,” sc. unless Thou gavest him intelligence? כּבד, heavy in multitude: in the Chronicles this is explained by גּדול.