It is narrated from Abu Huraira (may Allah be pleased with him) that he said: "Prohibition through suckling does not occur until it fills the intestines (i.e., until the stomach is filled)."
Hadith Referenceمسند الإمام الشافعي / كتاب النكاح / 1185
Hadith Takhrijصحیح اخرجه البيهقي : 7 / 456 - وفى المعرفة السنن والآثار له (4723) - وعبد الرزاق (13910) وابن ابی شيبة (17051)۔