Sunan an-Nasa'i, Volume 4, Book 34, Hadith 3757 (DarusSalam) ⓘ
It was narrated from Tawus that the Messenger of Allah made 'Umra and Ruqba binding.
أَخْبَرَنَا مُحَمَّدُ بْنُ حَاتِمٍ، قَالَ حَدَّثَنَا حِبَّانُ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ مُحَمَّدِ بْنِ إِسْحَاقَ، قَالَ حَدَّثَنَا مَكْحُولٌ، عَنْ طَاوُسٍ، بَتَلَ رَسُولُ اللَّهِ صلى الله عليه وسلم الْعُمْرَى وَالرُّقْبَى .
also referenced under: Hadith 3726 (Reference) & Book 34, Hadith 8 (In-Book)