"Whosoever intercedes for a good cause will have the reward thereof..." Sahih al-Bukhari 6028
Arabic hadith text
حَدَّثَنَا مُحَمَّدُ بْنُ الْعَلاَءِ، حَدَّثَنَا أَبُو أُسَامَةَ، عَنْ بُرَيْدٍ، عَنْ أَبِي بُرْدَةَ، عَنْ أَبِي مُوسَى، عَنِ النَّبِيِّ صلى الله عليه وسلم أَنَّهُ كَانَ إِذَا أَتَاهُ السَّائِلُ أَوْ صَاحِبُ الْحَاجَةِ قَالَ "اشْفَعُوا فَلْتُؤْجَرُوا، وَلْيَقْضِ اللَّهُ عَلَى لِسَانِ رَسُولِهِ مَا شَاءَ "
Translation
Narrated Abu Musa
Whenever a beggar or a person in need came to the Prophet, the Prophet would say "Help and recommend him and you will receive the reward for it, and Allah will bring about what he will through His Prophet's tongue