I heard my father saying, "Never did Messenger of Allah ﷺ assume Ihram except at the Mosque, that is, at the Mosque of Dhul-Hulaifa.  

أَنَّهُ سَمِعَ أَبَاهُ يَقُولُ مَا أَهَلَّ رَسُولُ اللَّهِ ﷺ إِلاَّ مِنْ عِنْدِ الْمَسْجِدِ يَعْنِي مَسْجِدَ ذِي الْحُلَيْفَةِ