Previously we saw a few cases of practical applications of the rule that truly righteous do not accidentally eat forbidden foods. This rule itself is based on the same rule about their animals.
Rabbi Pinchas ben Yair was on his way to redeem captives – which is one of the most important commandments – when he encountered the river Ginai. He said to the river, “Ginai, split your waters, so that I may cross through you.” The river answered, “You are trying to do the will of your Maker, but you may or may not succeed, while I will certainly accomplish the will of my Maker and continue to flow.” Rabbi Pinchas said, “If you do not split, I decree that water shall never flow again through you,” at which the river split.
There was a man with Rabbi Pinchas, bringing flour for matzah. “Split also for him!” - commanded Rabbi Pinchas, and the river obeyed. There also was an Arab merchant with them, and Rabbi Pinchas made the river split for him yet again.
When Rabbi Pinchas arrived at an inn, they poured barley for his donkey, but it refused to eat. They sifted and then cleaned the barley, but it still did not eat. “Perhaps you bought it from a source that cannot be trusted to separate the tithes,” - suggested Rabbi Pinchas - “The poor creature is going to perform the will of its Maker, so it should not be given forbidden foods.” Then the donkey ate.
But, when one buys grain for an animal, he needs not tithe it? - True, if he buys it initially for the animal. In this case, however, they bought it for the needs of Rabbi Pinchas, who was known to never accept presents, and thus the exemption from tithing did not apply.
Art: Willem Maris - A Herdboy With Donkeys On Scheveningen Beach