What is the meaning of the saying of the Prophet, peace and blessings be upon him: "And the Hijrah demolishes what came before it"?

This phrase means that migration (Hijra) is one of the causes for the forgiveness of sins. The proof for this is the hadith narrated by Muslim from Amr ibn al-Aas (may Allah be pleased with him), in which the Prophet (peace and blessings of Allah be upon him) said: "Do you not know that Islam demolishes what came before it, and that migration (Hijra) demolishes what came before it, and that Hajj demolishes what came before it?" This indicates that migration is a cause for wiping away errors and sins.