Allah, Glorified be His praise, says: "And mothers shall breastfeed their children for two full years, (this is) for the one who wishes to complete the nursing; and upon the one to whom the child is born (i.e. the father) is their provision and their clothing according to what is customary." [Surah al-Baqarah: 233]
And He said: "Then if they breastfeed (the child) for you, give them their payment." [Surah al-Talaq: 6]
It is narrated from Sayyidah Aishah (may Allah be pleased with her) that Hind (may Allah be pleased with her) said: O Messenger of Allah (peace and blessings be upon him), Abu Sufyan (may Allah be pleased with him) is a stingy man; is there any sin on me if I take something from his wealth? He (peace and blessings be upon him) said: "Take what suffices you and your child in a fair and customary manner." Al-Bukhari recorded it in the Sahih from the hadith of Sufyan al-Thawri, and Muslim recorded it through other chains from Hisham bin Urwah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النفقات / 15733