Here I led the Angels of Paradise in Salat just as in Bait al Muqaddas I led the previous Prophets in Salat. When I went into Sajdah, Allah called out, "I had made fifty Salat for each day incumbent upon the Prophets who came before you; and upon you and your Ummah, I make these incumbent too for these fifty Salat I have confirmed."
After the Salat, I continued on my back and while on the path, I met Prophet Ibrahim al‑Khalil. He did not ask me a single question.
Then I met Musa ibn `Imran. He asked me, "O' Muhammad what did you do?" I replied, "My Allah told me that he had made fifty daily Salat obligatory on the Prophets before me, and upon me and my Ummah too, He has made this amount obligatory."
Prophet Musa said to me, "O' Muhammad! Your Nation is the final and the weakest of all the Nations. Allah's commands must be followed, however your Nation does not have the ability to perform fifty daily Salat; thus, return to Allah and request Him to lighten the load on your Ummah."
I returned to Sidratul Muntaha and fell into prostration. I said, "O' Allah! You have made fifty daily Salat obligatory on my Ummah and me. However, my Ummah and I do not have the ability to perform this much. From your Holy Presence, I request a reduction in this."
Allah, Glorious and High ‑ reduced the number of Salat by ten.
I returned back and informed Musa what happened. He replied, "Go back as they do not have the power to perform even this much."
I returned once again, and Allah reduced the number of Salat by ten. I was going back when Musa said, "Still they do not have the ability to perform even this."
I once again returned, fell into sajdah, and asked for a reduction in the Salat. Allah once more reduced the number by ten.
I returned to where Musa was and told him what happened. Again he said to me, "Go back since they will not be able to even handle this."
I once again returned, fell into sajdah and again asked Allah for a reduction in the Salat. I said, "O' Allah, my Nation is weak and they will not have the ability to handle even this." Allah reduced the Salat by ten more. From a total of fifty Salat, only ten were made obligatory.
Again, I passed by Musa and he said, "Your Ummah does not have the ability to even handle ten Salat."
For the last time I returned and fell into sajdah. Allah reduced the Salat by five. I went to where Musa was and he said to me, "Your Ummah does not even have the ability to perform five daily Salat." I said to him, "I am embarrassed to go back to Allah again. I will just be patient in relation to these five Salat."
Then I heard a voice that said, "Since you have had patience, these five Salat will be counted as fifty Salat. Each Salat will be counted as ten Salat, and if one person from your Ummah performs a good act, then ten good acts will be written for him, but if he performs one bad act, then only that one bad act will be written in his record."
Imam Ja'far as‑Sadiq had said, "May Allah give Musa great reward since because of him, the daily (obligatory) Salat were reduced to only five."
From Bihar al-Anwar, Vol. 18, p. 330-331, Bab 3 - Ithbaat al-Mi
raaj wa maanaahu wa kayfiyyatuhu wa sifatuhu wa ma jaraa feehi wa wasf al-buraaq, Hadith 34.