Muwatta Imam Malik Book of Hajj, Hadith 1

Yahya related to me from Malik from Abd ar-Rahman ibn al-Qasim from his father from Asma bint Umays that she gave birth to Muhammad ibn Abi Bakr at al-Bayda. Abu Bakr mentioned this to the Messenger of Allah ﷺ and he said, "Tell her to do ghusl and then enter ihram."

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ الْقَاسِمِ، عَنْ أَبِيهِ، عَنْ أَسْمَاءَ بِنْتِ عُمَيْسٍ، أَنَّهَا وَلَدَتْ مُحَمَّدَ بْنَ أَبِي بَكْرٍ بِالْبَيْدَاءِ فَذَكَرَ ذَلِكَ أَبُو بَكْرٍ لِرَسُولِ اللَّهِ ﷺ فَقَالَ " مُرْهَا فَلْتَغْتَسِلْ ثُمَّ لِتُهِلَّ " .