´It was narrated that Umm Subyah Al-Juhaniyyah said:` "Often my hand would touch the hand of the Messenger of Allah while performing ablution from a single vessel." (Hasan) Abu `Abdullah bin Majah said: "I heard Muhammad say: 'Umm Subyah was Khawlah bint Qais. I mentioned that to Abu Zur`ah and he said: "It is true."
Hadith Referenceسنن ابن ماجه / كتاب الطهارة وسننها / 382
Hadith Gradingالألبانی:حسن صحيح | زبیر علی زئی:إسناده حسن
It is possible that this incident occurred before the command of veiling (hijab) was revealed, or perhaps she had such a relationship with the Prophet (sallallahu alayhi wa sallam) due to which veiling was not obligatory. And Allah knows best.
Source: Commentary on Sunan Ibn Mājah by Mawlānā ‘Atā’ullāh Sājid, Page: 382
Narrated Aishah, Ummul Muminin: My hands and the hands of the Messenger of Allah ﷺ alternated into one vessel while we performed ablution.
Shaykh Umar Farooq Saeedi
Explanation: There is no relationship of mahram established between Sayyidah Khawlah radi Allahu anha and the Messenger of Allah sallallahu alayhi wa sallam. This incident is perhaps from before the revelation of the verses of hijab in 6 AH.
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 78