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.  

أَتَى رَسُولُ اللَّهِ ﷺ قَبْرَ أُمِّهِ فَبَكَى وَأَبْكَى مَنْ حَوْلَهُ فَقَالَ رَسُولُ اللَّهِ ﷺ اسْتَأْذَنْتُ رَبِّي تَعَالَى عَلَى أَنْ أَسْتَغْفِرَ لَهَا فَلَمْ يُؤْذَنْ لِي فَاسْتَأْذَنْتُ أَنْ أَزُورَ قَبْرَهَا فَأُذِنَ لِي فَزُورُوا الْقُبُورَ فَإِنَّهَا تُذَكِّرُ بِالْمَوْتِ  

The Messenger of Allah ﷺ as saying: I forbade you to visit graves, but you may now visit them, for in visiting them there is a reminder (of death).  

قَالَ رَسُولُ اللَّهِ ﷺ نَهَيْتُكُمْ عَنْ زِيَارَةِ الْقُبُورِ فَزُورُوهَا فَإِنَّ فِي زِيَارَتِهَا تَذْكِرَةً