It is a Sunnah to visit graves as they remind one of death

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  

It was narrated from Ibn Mas’ud that the Messenger of Allah ﷺ said, “I used to forbid you to visit the graves, but now visit them, for they will draw your attention away from this world and remind you of the Hereafter.”  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ كُنْتُ نَهَيْتُكُمْ عَنْ زِيَارَةِ الْقُبُورِ فَزُورُوا الْقُبُورَ فَإِنَّهَا تُزَهِّدُ فِي الدُّنْيَا وَتُذَكِّرُ الآخِرَةَ  

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). (Using translation from Abū Dāʾūd 3235)   

قَالَ رَسُولُ اللَّهِ ﷺ «نَهَيْتُكُمْ عَنْ زِيَارَةِ الْقُبُورِ فَزُورُوهَا فَإِنَّهَا تُذَكِّرُكُمُ الْمَوْتُ»  

[Machine] The Messenger of Allah ﷺ said, "I used to prohibit you from visiting graves, but now I encourage you to do so, for it softens the heart, brings tears to the eyes, and reminds you of the hereafter. However, do not say anything that will bring harm."  

قَالَ رَسُولُ اللَّهِ ﷺ «كُنْتُ نَهَيْتُكُمْ عَنْ زِيَارَةِ الْقُبُورِ أَلَا فَزُورُوهَا فَإِنَّهُ يُرِقُّ الْقَلْبَ وَتُدْمِعُ الْعَيْنَ وَتُذَكِّرُ الْآخِرَةَ وَلَا تَقُولُوا هُجْرًا»  

[Machine] The Messenger of Allah, peace be upon him, said: "I used to forbid you from visiting graves, but whoever wishes to visit a grave, let him do so, as it softens the heart, brings tears to the eyes, and reminds of the Hereafter."  

قَالَ رَسُولُ اللَّهِ ﷺ «إِنِّي كُنْتُ نَهَيْتُكُمْ عَنْ زِيَارَةِ الْقُبُورِ فَمَنْ شَاءَ أَنْ يَزُورَ قَبْرًا فَلْيَزُرْهُ فَإِنَّهُ يُرِقُّ الْقَلْبَ وَيُدْمِعُ الْعَيْنَ وَيُذَكِّرُ الْآخِرَةَ»  

"نَهَيتُكُمْ عَنْ زِيَارَةِ الْقُبُورِ فَزُورُوهَا، فَإنَّهَا تُذَكِّرُكُمُ الْمَوْتَ".  

"كنتُ نَهَيتُكُمْ عَن زيَارَةِ القُبورِ ثُمَّ بَدَا لي فزُورُوهَا؛ فَإنهَا ترِق القَلبَ، وَتُدْمِعُ العَيْنَ، وَتُذَكِّرُ الآخِرَةَ، فَزُورُوا وَلَا تُقُولُوا هُجْرا".  

"قَدْ كُنتُ نَهيتكُمْ عن زِيارة القُبورِ- فَقَدْ أُذنَ لمحمَّدٍ فِي زِيارةِ قَبْرِ أُمِّهِ- فزُوروها فإِنَّهَا تُذَكِّرُكُم الآخِرةَ".  

"إِنِّى كُنْتُ نَهَيْتُكُمْ عَنْ زيَارَةِ الْقُبُورِ، ثُمَّ بَدَا لِى أَنَّهَا تُرِقُّ الْقَلْبَ وَتُدْمِعُ الْعَيْنَ وتُذَكِّر الآخِرَةَ فَزورُوهَا وَلا تَقُولُوا هُجْرًا).