Gittin 53B

ששקל בהן משקלות, כשרה! לא קשיא: הא בגופן, הא בכנגדן.

with which he weighed weights is fit? The Talmud answers: It is not difficult: This baraita is referring to a case where he weighs an object with the water itself, and therefore the water is disqualified. And this statement of Rava’s, that the water is fit, is referring to a case where he weighs an object against the water.

בגופן ⁠– מעשה קא עביד בהו; ואי היזק שאינו ניכר שמיה היזק, בדיני אדם נמי לחייב! אלא אידי ואידי בכנגדן; ולא קשיא ⁠– הא דאסח דעתיה. הא דלא אסח דעתיה.

The Talmud asks: If he weighs an object with the water itself, then he performs a real task with it, and if damage that is not evident is nevertheless categorized as damage, then he should also be liable according to human laws to pay for performing a task with the water. Rather, it is necessary to say that both this and that refer to a case where he weighed an object against the water, and still it is not difficult: This baraita is referring to a case where in the course of the weighing the object his attention was diverted from guarding the water, and owing to this lapse in attention the water became disqualified. And that statement of Rava’s is referring to a case where his attention was not diverted, and therefore the water did not become disqualified.

מתיב רב פפא: גזל מטבע, ונפסל; תרומה, ונטמאת; חמץ, ועבר עליו הפסח; אומר לו: ״הרי שלך לפניך״.

Rav Pappa raises an objection against Ḥizkiyya’s opinion from that which is taught in a baraita: If one robbed another of a coin and afterward the coin was rendered invalid by the government, or if he robbed another of teruma and it became ritually impure, or if he robbed another of leavened bread and Passover then elapsed over it, rendering it forbidden, in each of these cases the robber can return the item and say to the robbery victim: That which is yours is before you. Since the robber returned the stolen item, he is not required to compensate the victim of the robbery for his monetary loss, although the stolen items are currently of minimal or no value.