Based on what we mentioned above, that there is an obligation to anticipate the arrival of Moshiach with certainty, we have to understand a Gemara in both Ta’anis (17a) and Sanhedrin (22b) which discusses whether Kohanim are allowed to drink wine nowadays. The Gemara cites a machlokes between the Rabbonon and Rebbi. The Rabbonon say: If a Kohen knows which mishmor [group] and which Beis Av [family of Kohanim] he belongs to, then he only needs to refrain from drinking wine on the day that his group of Kohanim are scheduled to work in the Beis HaMikodsh. To ensure that he is able to help out with the avodah, he has to refrain from wine that day.
If, however, he doesn’t know which mishmor or beis av he belongs to, then he must refrain from drinking wine all year round. The reason being, it could be that on that particular day he will be needed for the avodah, and being as he doesn’t know when his turn is, he must be prepared every single day. (Although currently the Beis HaMikdosh is destroyed, it could be rebuilt any second).
Rebbi says, ideally he would agree to the opinion of the Rabbonon, אבל מה אעשה שתקנתו קלקלתו – but what can I do, many years have passed since the Beis HaMikdosh was destroyed, and we aren’t so worried that it will be rebuilt, therefore, a Kohen can drink wine all year round.
The Rambam (Hilchos Bias Mikdosh 1:7) rules like Rebbi, that if a Kohen doesn’t recognise his mishmor or beis av, strictly speaking he should refrain from drinking wine all year long, however, because it has been so long since the churban, it’s ok for such a Kohen to drink wine.
