أَخْبَرَنِي مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى، قَالَ حَدَّثَنَا خَالِدٌ، قَالَ حَدَّثَنَا شُعْبَةُ، قَالَ أَخْبَرَنِي ابْنُ أَبِي بُرْدَةَ، قَالَ سَمِعْتُ أَبِي يُحَدِّثُ، عَنْ أَبِي مُوسَى، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏"‏ عَلَى كُلِّ مُسْلِمٍ صَدَقَةٌ ‏"‏ ‏.‏ قِيلَ أَرَأَيْتَ إِنْ لَمْ يَجِدْهَا قَالَ ‏"‏ يَعْتَمِلُ بِيَدِهِ فَيَنْفَعُ نَفْسَهُ وَيَتَصَدَّقُ ‏"‏ ‏.‏ قِيلَ أَرَأَيْتَ إِنْ لَمْ يَفْعَلْ قَالَ ‏"‏ يُعِينُ ذَا الْحَاجَةِ الْمَلْهُوفَ ‏"‏ ‏.‏ قِيلَ فَإِنْ لَمْ يَفْعَلْ قَالَ ‏"‏ يَأْمُرُ بِالْخَيْرِ ‏"‏ ‏.‏ قِيلَ أَرَأَيْتَ إِنْ لَمْ يَفْعَلْ قَالَ ‏"‏ يُمْسِكُ عَنِ الشَّرِّ فَإِنَّهَا صَدَقَةٌ ‏"‏ ‏.‏

It was narrated from Abu Musa that the Prophet said: "Every Muslim must give charity." It was said: "What if he cannot find (anything to give)? "He said: "Let him work with his hands and benefit himself and give in charity." It was said: "What if he cannot do that?" He said: "Let him help someone who is in desperate need." It was said: "What if he cannot do that?" He said: "Let him enjoin good." It was said: "What if he cannot do that? He said: "Let him refrain from doing evil, for that is an act of charity." Translation Not Available

Book Ref: Sunan An Nisai Book 23 Hadith 2538
Web Ref:  Sunan An Nisai Vol 3 Book 23 Hadith 2539