It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) said: "Nursing does not establish prohibition except what takes place within the two years."
Abu Ahmad said: This is known (as narrated) by al-Haytham bin Jamil from Ibn Uyaynah with a connected chain (musnad), while others besides al-Haytham narrate it as mawquf on Ibn Abbas (may Allah be pleased with them both).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الرضاع / 15669