Consolation to the Messenger from Allaah

Perhaps, [O Muhammad], you would kill yourself with grief that they will not be believers.

[Qur'aan 26:3]

This is a consolation from Allaah to His Messenger (sallallaahu alayhi wa sallam) in regards to the lack of Imaan of those who did not believe in him from among the disbelievers just like He has said [in other Verses]:

Then is one to whom the evil of his deed has been made attractive so he considers it good [like one rightly guided]? For indeed, Allah sends astray whom He wills and guides whom He wills. So do not let yourself perish over them in regret. Indeed, Allah is Knowing of what they do.

[Qur'aan 35:8]

Then perhaps you would kill yourself through grief over them, [O Muhammad], if they do not believe in this message, [and] out of sorrow.

[Qur'aan 18:6]

Reference(s):

Tafsiir Ibn Kathiir