The _Sma”k_ teaches that believing in Moshiach is part of the first commandment.

Our sages say that after death, a person is asked: “Did you await Moshiach?” But where is this mitzvah actually written in the Torah?

He explains: The first commandment says, _“I am Hashem your G-d who took you out of Egypt.”_ Just as we must believe that Hashem took us out of Egypt, so too we must believe that _“I am Hashem your G-d who will gather you and redeem you in the future.”_

In other words, the mitzvah to believe in Hashem includes both what He did in the past and what He promised to do in the future with Moshiach.