Clarifying that it is better to enter Ihram when a person's mount sets off with him, heading towards Makkah, not straight after the two rak'ah Sahih Muslim 1187 c
Arabic hadith text
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَلِيُّ بْنُ مُسْهِرٍ، عَنْ عُبَيْدِ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، - رضى الله عنهما - قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلمإِذَا وَضَعَ رِجْلَهُ فِي الْغَرْزِ وَانْبَعَثَتْ بِهِ رَاحِلَتُهُ قَائِمَةً أَهَلَّ مِنْ ذِي الْحُلَيْفَةِ .
Translation
Ibn 'Umar (Allah be pleased with them) reported that the Messenger of Allah (ﷺ) pronounced Talbiya in Dhu'l-Hulaifa as he put his feet in the stirrup and his camel stood up and proceeded.