Al-Matalib al-'Aliyah 573 — Completing the obligatory

It is narrated from a servant (man or woman) of the Messenger of Allah (peace and blessings be upon him) that the Prophet (peace and blessings be upon him) used to (often) ask him: "Do you have any need?" Until one day he said: "O Messenger of Allah, I have a need." He (peace and blessings be upon him) asked: "What is your need?" He said: "My need is that you intercede for me on the Day of Resurrection (that is, become the means of my forgiveness)." He (peace and blessings be upon him) asked (expressing wonder and joy): "Who guided you to this (lofty aim)?!" He replied: "My Lord (put this into my heart)." He (peace and blessings be upon him) said: "Then help me (in attaining this wish of yours and in your becoming deserving of my intercession) through abundant prostration (that is, by praying abundantly)."
Imam Ahmad recorded this hadith in his Musnad, and Allamah al-Albani along with other hadith scholars declared its chain hasan (good) or sahih (authentic).