His statement, “and drink it in three sips,” means that it is sunnah to drink in three breaths (1), for when the Prophet ﷺ drank, he drank by sipping, and he said: “It is more satisfying and healthier.” (2) This has three benefits. One should sip rather than gulp, because water is only drunk when one needs it—when one is thirsty. Thirst is an inflammation and heat in the stomach; therefore, when water enters it in gulps, it affects it, because the cold strikes the heat. But when it is sipped, what goes down is light and gradual, acquiring warmth as it passes from the mouth to the stomach; thus, it reaches the stomach warm and suitable for it.
It should be drunk in three portions, owing to the Prophet’s statement: “It is more satisfying, healthier, and more wholesome.” For this reason, those who know say that if you find someone extremely thirsty, do not give him water all at once; if you do so, he may perish. Rather, give him one drink and one gulp, then wait a little, then give him the second, and so on, lest he perish.
His statement, “by sipping,” applies to water. As for milk, broth, and the like, they should be drunk in gulps. The difference between them is evident: water is thin and contains no fat or anything nourishing for the stomach, so it is more appropriate for it to reach the stomach little by little. Milk and similar drinks, on the other hand, may be drunk in gulps, but in three breaths.