There are two disputes between Rashi and the Ramban regarding the punishment of the sin of the golden calf, which the Brisker Rav connects together.
Firstly, Rashi is of the opinion that Moshe came down and saw the sin on the 17th Tamuz, and punished the sinners on the 18th. But the Ramban holds that Moshe punished them on the same day that he came down; the 17th. The second machlokes regards the punishment itself. Rashi (33;20) holds that the punshment followed normal rules of idolatry – those which receiced a warning before sinning were to be killed by the sword like an ‘ir hanidachas’ (community who did idolatry) and those who did not receive a warning were killed ‘bidei shamayim.’ The Ramban,however, holds that the punishment was an exception to the normal rules of punishment for idolatry, specific for this sin – hence the ability to punish without warning of the sin. The Brisker Rav connects the 2 disputes up. The halacha is that a capital case’s sentence cannot be passed on the same day that the case is brought to court. Thus, according to rashi, the people were only punished the next day – for the normal procedures applied here. But according to the Ramban, since this was a one-off and did not follow normal court rules, (a’hora’as sha’ah’)the punishment could be administered the same day.
I then found that this machlokes Rashi-Ramban is actually a machlokes between Rav and Levi in gemarra Yoma 66b, and Rashi is quoting and siding with one opinion, whilst the Ramban is citing the other opinion (Ramban 32;27).