The 55th prohibition is that we are forbidden from distancing ourselves from Egyptians by refusing to marry them once they have converted to Judaism.1
The source of this commandment is G‑d's statement,2 "do not despise the Egyptian."
The details of these two mitzvos, i.e., that of the Egyptian and that of the Edomite,3 are explained in the eighth chapter of Yevamos and the end of Kiddushin.4