Nazir 32 - They knew when the Temple would be destroyed
If one became a nazir, but kept drinking wine - hoping, perhaps, that his vow will be annulled - but a Sage affirmed his vow - he continues his period of being a nazir and finishes it. However, the Sages imposed upon him a penalty: he cannot even ask about annulment until he behaves properly for as many days as he previously violated by drinking wine. If after all a Sage annulled his vow of being a nazir, and he already separated an animal for the concluding sacrifices - we are back to the argument between Beit Hillel and Beit Shammai. Beit Hillel simply allow the animal to go back to its flock.
If one thought that he had an animal to conclude his nazir's vow and declared himself a nazir, but then discovered that the animal was stolen - if it was stolen before the vow, then he is not a nazir. If it was stolen after his vow, then he was a valid nazir for the time that the animal was still in his possession, so his vow is valid.
Nachum HaMede made this mistake: he annulled all nazir vows for people who made them close to the Temple destruction. The Sages corrected him: if they vowed before the destruction, their vows were in fact valid. But they knew that the Second Temple would be destroyed 490 ( seventy weeks ) years after the the first one, so how could they vow in earnest?! - They still hoped that their period of being a nazir will finish while the Temple was standing.
Art: In The Wine Cellar by Jan David Col