Abu Hurairah:
The Messenger of Allah (ﷺ) visited his mother's grave and wept and cause those around him to weep. The Messenger of Allah (ﷺ) then said: I asked my Lord's permission to pray for forgiveness for her, but I was not allowed. I then asked His permission to visit her grave, and I was allowed. So visit graves, for they make one mindful of death.