It is narrated from Abu Ja'far Muhammad bin Ali (Imam al-Baqir) (may Allah have mercy on him) that he said: "Only obligatory charity (zakah) has been made forbidden for us."
Imam al-Shafi'i (may Allah be pleased with him) said: "Sayyiduna Ali and Sayyidah Fatimah (may Allah be pleased with them both) gave their wealth in charity to Banu Hashim and Banu al-Muttalib, and that (was permissible) because it was voluntary charity."
The Shaykh (Imam al-Bayhaqi) (may Allah have mercy on him) said: "This (narration) has already passed."
Imam al-Shafi'i (may Allah be pleased with him) said: "The Prophet (peace and blessings be upon him) accepted a gift from the charity that had been given to Sayyidah Barirah (may Allah be pleased with her), and that is because from Barirah (may Allah be pleased with her) it was a voluntary gift, not charity."
Sayyidah Aishah (may Allah be pleased with her) said: Meat was brought to the Prophet (peace and blessings be upon him) and it was said: "O Prophet of Allah, this is meat that was given in charity to Barirah." He (peace and blessings be upon him) said: "It is charity for Barirah and a gift for us."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الصدقات / 13247