Is it permissible for a Muslim to visit the graves of disbelievers?

It is permissible to visit the grave of a non-Muslim for the purpose of reflection only, as it is reported that the Prophet, peace and blessings be upon him, visited his mother's grave and sought his Lord's permission to do so. When visiting the grave of a disbeliever, one should not greet him or supplicate for him; rather, he should be given tidings of the Fire, as narrated in the hadith of Sa'd ibn Abi Waqqas and the hadith of Abu Hurayrah.