Sahih Bukhari Volume 2, Book 15, Hadith 1010

وَقَالَ عُمَرُ بْنُ حَمْزَةَ حَدَّثَنَا سَالِمٌ، عَنْ أَبِيهِ، رُبَّمَا ذَكَرْتُ قَوْلَ الشَّاعِرِ وَأَنَا أَنْظُرُ، إِلَى وَجْهِ النَّبِيِّ صلى الله عليه وسلم يَسْتَسْقِي، فَمَا يَنْزِلُ حَتَّى يَجِيشَ كُلُّ مِيزَابٍ‏.‏ وَأَبْيَضَ يُسْتَسْقَى الْغَمَامُ بِوَجْهِهِ ثِمَالَ الْيَتَامَى عِصْمَةً لِلأَرَامِلِ وَهْوَ قَوْلُ أَبِي طَالِبٍ‏

Salim's father (Ibn 'Umar) said, "The following poetic verse occurred to my mind while I was looking at the face of the Prophet (p.b.u.h) while he was praying for rain. He did not get down till the rain water flowed profusely from every roof-g utter: And a white (person) who is requested to pray for rain and who takes care of the orphans and is the guardian of widows... And these were the words of Abu Talib."