Mishnah: One must wash his hands by pouring 1/4th-log of water over them before eating non-sacred food, and for tithes and for teruma; but for eating sacrificial food one must immerse one’s hands in purification waters, such as those of a mikveh. And with regard to one who wishes to touch the purification waters of the red heifer used for sprinkling, concerning which the rabbis ordained further measures of sanctity, if one’s hands were rendered impure even by rabbinical ritual impurity, which usually only renders the hands impure, his entire body is rendered impure, and he must immerse himself in a mikveh.
טבל לחולין, הוחזק לחולין — אסור למעשר. טבל למעשר, הוחזק למעשר — אסור לתרומה. טבל לתרומה, הוחזק לתרומה — אסור לקודש. טבל לקודש, הוחזק לקודש — אסור לחטאת. טבל לחמור — מותר לקל. טבל ולא הוחזק — כאילו לא טבל.
The Mishnah continues to list additional differences between various levels of ritual purity: If one immersed for the purpose of eating non-sacred food, he assumes a presumptive status of ritual purity for non-sacred food, and it is prohibited for him to eat tithes, as he did not purify himself with the intention of eating tithes. If one immersed to eat tithes, he assumes a presumptive status for tithes, but he is prohibited from eating teruma. If one immersed for teruma, he assumes a presumptive status for teruma, but he is prohibited from eating sacrificial food. If he immersed for sacrificial food, he assumes a presumptive status for sacrificial food, but he is prohibited from coming in contact with the purification waters. The principle is as follows: One who immersed to eat a food in a stringent category is permitted to eat a food in a lenient one. Another principle: One who immersed without the intention to assume a presumptive status of ritual purity, i.e., one who immersed but did not intend to purify himself, it is as though he has not immersed at all.