Daf Yomi - Yoma 79 - Eating and Drinking

The Rama (197) brings an opinion that holds that there is not an obligation for birchas hamazon unless one eats and drinks. Eating alone is not sufficient for there to be an obligation. This is learned from the possuk ואכלת ושבעת וברכת. They learn that the word ושבעת is referring to drinking. The Torah is telling us that both are needed for bentching. The שער הציון brings from a Tosfos Yeshonim on our daf that the halacha is not in accordance with that opinion and that there is an obligation for a brocha acharona for eating and one for drinking and both together are not required.