Sunan Ibn Majah, Volume 1, Book 4, Hadith 764 (DarusSalam) ⓘ
It was narrated from 'Aishah that: The Prophet scratched some spittle from the prayer direction of the mosque.
حَدَّثَنَا عَلِيُّ بْنُ مُحَمَّدٍ، حَدَّثَنَا وَكِيعٌ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ، أَنَّ النَّبِيَّ ـ صلى الله عليه وسلم ـ حَكَّ بُزَاقًا فِي قِبْلَةِ الْمَسْجِدِ .
also referenced under: Hadith 764 (Reference) & Book 4, Hadith 30 (In-Book)