The soundness of Ihram for the woman in Nifas; It is recommended for her to perform Ghusl before entering Ihram, and the same applies to one who is menstruating Sahih Muslim 1210
Arabic hadith text
حَدَّثَنَا أَبُو غَسَّانَ، مُحَمَّدُ بْنُ عَمْرٍو حَدَّثَنَا جَرِيرُ بْنُ عَبْدِ الْحَمِيدِ، عَنْ يَحْيَى بْنِ، سَعِيدٍ عَنْ جَعْفَرِ بْنِ مُحَمَّدٍ، عَنْ أَبِيهِ، عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ، - رضى الله عنهما - فِي حَدِيثِ أَسْمَاءَ بِنْتِ عُمَيْسٍ حِينَ نُفِسَتْ بِذِي الْحُلَيْفَةِ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلمأَمَرَ أَبَا بَكْرٍ - رضى الله عنه - فَأَمَرَهَا أَنْ تَغْتَسِلَ وَتُهِلَّ .
Translation
Jabir b. `Abdullah (Allah be pleased with them) reported that when Asma' bint `Umais gave birth (to a child) in Dhu'l-Hulaifa. Allah's Messenger (ﷺ) commanded Abu Bakr (to convey to her) that she should take a bath and enter into the state of Ihram.