Orlah 2:13

If leather goods were oiled using ritually impure oil and then they were oiled using ritually clean oil, or vice versa, Rabbi Eliezer says the status of the item follows the first oil used; the Sages say it follows the last oil used.

Orlah 2:14

If leaven of terumah and leaven of mixed species from a vineyard fell into dough and neither one was sufficient to leaven the dough by itself but combined they are, it is permitted to kohanim and prohibited to others; Rabbi Shimon permits it to everyone.