´It was narrated that 'Aishah said:` "If anyone tells you that the Messenger of Allah urinated while standing, do not believe him, for I (always) saw him urinating while sitting down."
Hadith Referenceسنن ابن ماجه / كتاب الطهارة وسننها / 307
The Mother of the Believers, Aisha (radi Allahu anha), is rejecting based on her knowledge; she is describing the usual practice.
Explanation & Benefits
Maulana Ataullah Sajid
Commentary: This negation by Aisha (radi Allahu anha) is according to her own knowledge, because in the house the Prophet (sallallahu alayhi wa sallam) would always urinate sitting in the toilet. In the previous hadith, Hudhayfah (radi Allahu anhu) narrated an incident that took place outside the house, of which the Mother of the Believers was not aware; therefore, both are correct in their respective contexts.
Source: Commentary on Sunan Ibn Mājah by Mawlānā ‘Atā’ullāh Sājid, Page: 307