It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that performing ablution after eating food was mentioned in his presence. On one occasion al-A'mash also said: and cupping for the fasting person (was mentioned). He said: Ablution is due to what comes out, not to what goes in; and the breaking of the fast is due to what goes in, not to what comes out.
This is also narrated from the Prophet (peace and blessings be upon him), but it is not established.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 567
Hadith Gradingمحدثین:صحيح لغيرهٖ
Hadith Takhrij«صحيح لغيرهٖ۔ أخرجه عبد الرزاق 653»