Why was it forbidden for the Prophet's household (Ahl al-Bayt) - may Allah bless him and grant him peace - to receive sadaqat (charity) and zakat (obligatory alms)?

Charity (sadaqah) was forbidden for Muhammad and the family of Muhammad because it is the impurities of people, and a purification for their wealth and souls. Scholars have explained this by citing the honor of prophethood, the elevated status of the Prophet, peace and blessings be upon him, and to preserve his position from being surpassed by those lower than him. It was also to prevent the polytheists from slandering him, for he never asked for a wage for his call.