Al-Kahf 18:6

FalaAAallaka bakhiAAun nafsaka AAalaatharihim in lam yu/minoo bihatha alhadeethiasafa

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

So, (O Prophet) perhaps you are going to kill yourself after them, out of grief, if they do not believe in this discourse.