Sunan an-Nasa'i, Volume 3, Book 24, Hadith 2718 (DarusSalam) ⓘ
It was narrated that 'Aishah said: "We went out with the Messenger of Allah around the time of the new moon of Dhul-Hijjah, and the Messenger of Allah said: 'Whoever wishes to enter Ihram for Hajj, let him do so, and whoever wishes to enter Ihram for 'Umrah, let him do so'"
أَخْبَرَنَا يَحْيَى بْنُ حَبِيبِ بْنِ عَرَبِيٍّ، عَنْ حَمَّادٍ، عَنْ هِشَامٍ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ، قَالَتْ خَرَجْنَا مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم مُوَافِينَ لِهِلاَلِ ذِي الْحِجَّةِ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ شَاءَ أَنْ يُهِلَّ بِحَجٍّ فَلْيُهِلَّ وَمَنْ شَاءَ أَنْ يُهِلَّ بِعُمْرَةٍ فَلْيُهِلَّ بِعُمْرَةٍ " .
also referenced under: Hadith 2717 (Reference) & Book 24, Hadith 0 (In-Book)