[If one says:] “I am a nazir on condition that I [be permitted to] drink wine,” or “contract tumah from the dead” —- he is a nazir and is prohibited in all of them. [If he says:] “I know that there is nezirus, but I did not know that a nazir is forbidden wine” —- he is forbidden. But R’ Shimon permits [him]. “I know that a nazir is forbidden wine, but I thought that the Sages would permit it for me since I cannot live without wine,” or “since I bury the dead” —- he is permitted. But R’ Shimon forbids [him].