Final answer:
Muhammad fled Mecca and later returned to reclaim and cleanse the city, proclaiming Mecca as the holiest city in Islam and the site for the hajj pilgrimage.
Step-by-step explanation:
After the significant event known as the Hijrah, wherein Muhammad fled to Medina to escape an assassination attempt, he later returned and took the city of Mecca.
Upon his return, Muhammad cleansed the Kaaba within Mecca of idols, reestablishing the pre-Islamic monotheistic worship of Ibrahim (Abraham).
Consequently, Muhammad proclaimed Mecca to be the holiest city in Islam, designating it as the direction of prayer (qibla) for Muslims and the destination for the pilgrimage (hajj).