Sayyidah Asma' bint Umays (may Allah be pleased with her) said that she entered postnatal bleeding at Dhu al-Hulayfah with (the birth of) Muhammad bin Abi Bakr (may Allah be pleased with them both). Sayyiduna Abu Bakr (may Allah be pleased with him) asked the Prophet (peace and blessings be upon him) about this, and he (peace and blessings be upon him) commanded: "She should take a ritual bath (ghusl) and say the talbiyah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8942