Reference for Menachot 60:16
הא איתמר עלה אמר רבי שמואל בר נחמני אמר רבי יוחנן הלכה כרבי שמעון שזורי ואם איתא הוא נמי לימא
R'Simeon of Shezur says, Even on a weekday one need only ask [the seller] about it and eat it by his word.<span class="x" onmousemove="('comment',' In the special circumstances, because of the loss involved and the produce being demai (i.e., produce that had been bought from an 'am ha-arez who was not trusted with regard to the separation of the tithes) , the Rabbis permitted the owner to enquire of the seller about it and to rely upon his word if the seller assured him that he had separated the various dues. If this occurred on the Sabbath it would certainly be permitted to ask the seller about the produce and to rely upon his word, for the honour of the Sabbath (v. Dem. l.c.) , but according to R. Simeon of Shezur this is permitted even on a weekday.');"><sup>15</sup></span> But since it was reported in that connection that R'Johanan said, The halachah follows R'Simeon of Shezur in the case of 'The dangerous ill man' and in 'The terumah separated from the tithe of demai produce',<span class="x" onmousemove="('comment',' Keth. 55a, and Hul. 75b.');"><sup>16</sup></span>