Al-Rabi' informed us that Imam al-Shafi'i (may Allah have mercy on him) said: Aishah (may Allah be pleased with her) ordered that he be suckled ten times, because that is the greatest number of sucklings, and five were not completed for him, so he did not come in to her. Perhaps Aishah's (may Allah be pleased with her) statement about the ten sucklings, that they were abrogated by five known ones, escaped Salim.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الرضاع / 15639