It was narrated that Ibn 'Abbas (رضي الله عنه) said:

Some men shaved their heads on the day of al-Hudaibiyah and others cut their hair. The Messenger of Allah (ﷺ) said: "May Allah have mercy on those who shaved their heads.” They said: O Messenger of Allah, and those who cut their hair? He said: "May Allah have mercy on those who shaved their heads.” They said: O Messenger of Allah, and those who cut their hair? He said: "May Allah have mercy on those who shaved their heads.” They said: O Messenger of Allah, and those who cut their hair? He said: "And those who cut their hair." They said: What is special about those who shaved their heads, O Messenger of Allah, that you prayed for mercy more for them? He said: “They did not doubt." Then the Messenger of Allah (ﷺ) left.