Tohoros 5:5

Let’s say that there were two paths, one ritually unclean and the other ritually clean. Someone walked on one of these paths and then prepared ritually-clean food, and then another person walked on the other path and prepared ritually-clean food. Rabbi Yehuda says that if each of these people asked for a ruling, then each is ruled to be clean but if they jointly asked for a ruling, both are ruled unclean. Rabbi Yosi says that in either case they are both deemed unclean.

Tohoros 5:6

Let’s say that there were two loaves, one ritually unclean and the other ritually clean. Someone ate one of these loaves and then prepared ritually-clean food, and then another person ate the other loaf and prepared ritually-clean food. Rabbi Yehuda says that if each of these people asked for a ruling, then each is ruled to be clean but if they jointly asked for a ruling, both are ruled unclean. Rabbi Yosi says that in either case they are both deemed unclean.