Imam al-Shafi'i (may Allah have mercy on him) said: "The view that Ata' (may Allah have mercy on him) held is that the expiation of an oath suffices him in this (case). Whoever holds this view has said the same about everything in which he breaks his oath, except freeing a slave or divorce. This is also the view of Sayyidah Aishah (may Allah be pleased with her), and the view of a number of the Companions of the Prophet (peace and blessings be upon him) (may Allah be pleased with them)."
Mansur bin Abd al-Rahman, a man of Banu Abd al-Dar, narrates from his mother Safiyyah (may Allah be pleased with her) that she heard Sayyidah Aishah (may Allah be pleased with her) when she was asked about a person who says: "My wealth is in the way of Allah," or "All my wealth is for the Ka'bah": what is its expiation? Sayyidah Aishah (may Allah be pleased with her) said: "Its expiation is the same as that of an oath."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأيمان / 20036