Hadhrat Aa'isha (r.a.) says: "After spending the night, Rasulullaah (s.a.w.) would be summoned (to salaah) by Bilaal (r.a.) calling out the Adhaan. He would then get up and take a bath. I would then see the water dripping on his cheek and beard as he left for salaah, after which I would hear him weep in salaah."
Abu Ya'la, reporting from reliable sources as confirmed by Haythami (Vol.2 Pg.89).
Hadhrat Ubayd bin Umayr (r.a.) once asked Hadhrat Aa'isha (r.a.): "Tell me what the most remarkable incident that you saw with Rasulullaah (s.a.w.)." Hadhrat Aa'isha (r.a.) was silent for awhile and then she said, "One night Rasulullaah (s.a.w.) said to me, 'Do excuse me to worship my Rabb tonight.' 'By Allaah!' I replied, 'While I love to be near you, I also love anything that pleases you.' Rasulullaah (s.a.w.) then stood up, performed wudhu and started performing salaah. He wept so much as he was sitting that his lap became wet (with tears). He then continued weeping until his beard was drenched. He had then eventually wept so much more that the ground around him became soaked. When Bilaal (r.a.) came to inform him that the time for salaah had arrived, he saw Rasulullaah (s.a.w.) weeping and asked, '0 Rasulullaah ! Why do you weep so much when Allaah has forgiven all your previous and future errors?' Rasulullaah (s.a.w.) replied, 'Should I then not be a grateful slave? A tremendous verse has been revealed to me tonight. Woe be to the person who recites it without pondering over it: (The verse is)
"Verily in the (perfect and wonderful) creation of the heavens and the earth (and whatever is within these) and in the alternation (changing) of the night and day are signs (that show Allaah's great power) for those who have intelligence (who care to ponder). (Those who have intelligence are) They who remember Allaah while standing, sitting and lying down (they do not forget Allaah at any time), and they think about the creation of the heavens and earth (so that they may be able to see Allaah's greatness in this). (Then, amazed by Allaah's creation, they say) "Our Rabb You have not created all this without a purpose! (These things certainly display Your power and greatness and have not been created in vain). We glorify Your purity (none can ever be equal to You) so save us from the punishment of the Fire (of Jahannam) ... " {Surah Al-Imraan, verses 190+ }
Ibn Hibbaan, as quoted in Targheeb wat Tarheeb (Vo1.3 Pg.32).
(From 'Hayatus Sahabah' by Maulana Muhammad Yusuf Khandhlawi)