That when they were present with the Messenger of Allah in Al-Madinah, he sent the Hadi, and whoever wanted to enter Ihram did so, and whoever did not want to, did not.  

عَنْ جَابِرٍ أَنَّهُمْ كَانُوا إِذَا كَانُوا حَاضِرِينَ مَعَ رَسُولِ اللَّهِ ﷺ بِالْمَدِينَةِ بَعَثَ بِالْهَدْىِ فَمَنْ شَاءَ أَحْرَمَ وَمَنْ شَاءَ تَرَكَ