Barzillai’s story is here given. We very well remember how that he provided victuals for king David (v. 32), when he was fleeing Israel because of Absalom, who had declared himself king.
Barzillai was kind to king David, such that when king David returned as king, he offered him the opportunity of dining with him in Jerusalem for as long as he wanted (v. 33-34). This goes to show the those we do good for today might be in a position to also do good to us tomorrow.
Let us therefore not be weary in well doing: for in due season we shall reap, if we faint not (Gal 6:9-10).