R. Yehudah says: He may multiply (wives) for himself so long as they do not "turn his heart," it being written "that his heart not turn astray."
R. Shimon says: He should not marry even one that turns his heart astray. If so, why is it written "he shall not multiply himself wives" — even one (so virtuous as) Avigayil.
"and silver and gold he shall not multiply for himself overmuch": I might think, (not) even to provision the army; it is, therefore, written "he shall not multiply for himself" — but he may multiply it to provision the army.