[Machine] Imam Al-Shafi'i, may Allah have mercy on him, said regarding the statement of Hafsa to the Prophet ﷺ , "You have not made it permissible for yourself from your umrah," meaning from the state of ihram with which you began. They (the Companions) had the same intention (to perform umrah) and Allah knows best. So he (the Prophet) said, "I have cut my hair and put on regular clothing (indicating the end of the state of ihram) and I have adopted the practices of hajj. I will not make it permissible (to engage in marital relations) until I slaughter the sacrificial animal," meaning the Prophet will not engage in marital relations until he has completed his hajj. This is because it was revealed to him (the Prophet) that anyone who is performing hajj with a sacrificial animal, their state of ihram will end.  

قَالَ الشَّافِعِيُّ رَحِمَهُ اللهُ فِي قَوْلِ حَفْصَةَ لِلنَّبِيِّ ﷺ وَلَمْ تَحْلِلْ مِنْ عُمْرَتِكَ تَعْنِي مِنْ إِحْرَامِكِ الَّذِي ابْتَدَأْتَهُ وَهُمْ بِنِيَّةٍ وَاحِدَةٍ وَاللهُ أَعْلَمُ فَقَالَ لَبَّدْتُ رَأْسِي وَقَلَّدْتُ هَدْيِي فَلَا أَحِلُّ حَتَّى أَنْحَرَ يَعْنِي وَاللهُ أَعْلَمُ حَتَّى يَحِلَّ الْحَاجُّ؛ لِأَنَّ الْقَضَاءَ نَزَلَ عَلَيْهِ أَنْ يَجْعَلَ مَنْ كَانَ مَعَهُ هَدْيٌ إِحرَامَهُ حَجًّا