It was narrated from Jabir:

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.

أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ أَبِي الزُّبَيْرِ، عَنْ جَابِرٍ، أَنَّهُمْ كَانُوا إِذَا كَانُوا حَاضِرِينَ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم بِالْمَدِينَةِ بَعَثَ بِالْهَدْىِ فَمَنْ شَاءَ أَحْرَمَ وَمَنْ شَاءَ تَرَكَ ‏.‏