Matthew Poole and continuators on 1 Samuel 16:20

20 And Jesse took an ass laden with bread, and a bottle of wine, and a kid, and sent them by David his son unto Saul

This Present, though in our times it would seem contemptible, yet was very agreeable to the usage of those times, and to the condition of Iesse, which was but mean in the World. And it seems to have been the Custome of those Times, as it is yet in the Eastern Countries (when they made their appearance before Princes, or great Persons, to bring a Present; (See Gen. 32. 20. Gen. 43. 25, 26. and elsewhere.) To which civil Custome, that Religious Precept seems consonant, Exod. 23. 15. Deut. 16. 16. None shall appear before me empty. And he might send it; partly, as a Testimony of his respect to his Soveraign; and partly, to gain David favour and acceptance with him; being sensible, that he was going into a place and state of hazzard; but knowing Saul's furious temper, he durst not refuse to send him; and he sent him the more willingly, because this seemed a most likely means to accomplish God's Promise of the Kingdome, and to prepare him for it.