Yerushalmi Berakhot 8:7 ירושלמי ברכות ח׳:ז׳

MISHNAH: He who ate, forgot, and did not recite Grace. The House of Shammai say, he should return to his place¹⁶⁴The place of the meal. and recite. The House of Hillel say, he should recite at the place where he remembers it. How long¹⁶⁵After the end of the meal, so that he should not by guilty of disregarding a biblical commandment. may he recite? Until the food is digested in his bowels.

HALAKHAH: Rebbi Justus bar Shunem¹⁶⁶A late Amora, student of Rebbi Mana II. said: Two Amoraïm, one proposed the reason of the House of Shammai and the other proposed the reason of the House of Hillel. He who proposed the reason of the House of Shammai: If he had forgotten there a wallet full of precious stones and pearls, would he not go back and retrieve his wallet? Here also, let him return to his place and recite Grace. He who proposed the reason of the House of Hillel: A worker who worked at the top of a date palm or at the bottom of a cistern, would one bother him to return and recite Grace? No, he should recite at the place where he remembers. So here also, he should recite at the place where he remembers¹⁶⁷In the formulation here, it is agreed that a worker at a dangerous place does not have to return (a) to expose himself to unnecessary danger and (b) to spend unproductive time at the expense of his employer who is required to pay his entire day. In the Babli (53b), the entire discussion is a baraita and the argument of the House of Hillel precedes that of the House of Shammai. Hence, its implication is that the House of Shammai require the worker to return to his dangerous place and his employer to pay for the time lost. In this case, it seems that the Yerushalmi reports a deliberate change from earlier practice in order to embody a change in labor law..

How long may he recite? Rebbi Ḥiyya in the name of Samuel, until the food in his bowels is digested. But the sages say, all the time that he is thirsty because of that meal¹⁶⁸Presumably, if he did not drink during the meal.. Rebbi Yoḥanan says, until he gets hungry again¹⁶⁹The Babli (53b) quotes R. Yoḥanan as is he quoted here and attributes the statement of the Sages (that would guide practice here) to R. Simeon ben Laqish, whose opinion carries less weight than that of R. Yoḥanan. Another statement of R. Simeon ben Laqish, who gives as maximum the time it would take to walk four mil, 1 hour 12 min., has no parallel in the Yerushalmi. The difference between the Galilean יתאכל and the Babylonian יתעכל is dialectal; the Babylonian Mishnah has יתעכל. Since Samuel was a medical doctor, his explanation “until the food was digested” may have been practical for him; it certainly is not practical for everybody else. It is therefore not necessary to say that R. Yoḥanan is more restrictive than the Mishnah (as is the opinion of the student of Rabbenu Jonah in his commentary on Alfassi.).