When the Quraish noticed that an open invitation was being given to Islam and idolatry was being openly condemned and criticized, they could not tolerate this. They thus prepared to show enmity and hostility to the one who invited to One Allah, and they prepared to oppose tauheed (proclaiming the oneness of Allah Ta‘ala). They resolved to cause such harm and pain to Rasulullah (sallallahu ‘alaihi wasallam) that he would be dissuaded and refrain from inviting people towards Islam.
Hazrat Muneeb Ghaamidi (radhiyallahu ‘anhu) relates, “I once observed Rasulullah (sallallahu ‘alaihi wasallam) addressing people and saying to them, ‘O people! Say Laa ilaaha illallaah, you will be successful.’ However, some wretched people were hurling abuse at him, some were spitting at him and others were flinging sand at him. They continued in this manner until the afternoon, when a young girl carrying water arrived and washed the blessed face and hands of Rasulullah (sallallahu ‘alaihi wasallam). When I enquired as to who the young girl was, I was informed that she was the daughter of Rasulullah (sallallahu ‘alaihi wasallam), Hazrat Zainab (radhiyallahu ‘anha).”
(Extracted from Seeratul Mustafa pg. 203)