The Messenger of Allah said: "I had prohibited you from visiting the graves. But Muhammad was permitted to visit the grave of his mother: so visit them, for they will remind you of the Hereafter."
Jami` at-Tirmidhi Book 10, Hadith 90
← Previous Hadith "The Messenger of Allah passed by the graves of Al-Madinah, so he turned his face towards them and said: (As-Salamu alaikum ya ahlul-qubur! Yaghfirul-lahu lana wa lakun, antum salafuna wa nahnu bil-athar.) 'Peace be upon you O inhabitants of the grave! May Allah forgive us and you; you are our predecessors and we are to follow you.'"

Jami` at-Tirmidhi Book 10, Hadith 89 Next Hadith → "Abdur-Rahman bin Abi Bakr died in Al-Hubshi" He said: "He was carried to Makkah to be buried there. So when Aishah arrived she went to the grave of Abdur-Rahman bin Abi Bakr and she said: "We were like two drinking companions of Jadhimah for such a long time that they would say: 'They will never part.' So when we were separated it was as if I and Malik - due to the length of unity - never spent a night together."

Jami` at-Tirmidhi Book 10, Hadith 91