Abu Musa al-Ash'ari (may Allah be pleased with him) narrates from the Prophet (peace and blessings be upon him) that he (peace and blessings be upon him) said: "Charity is due upon every Muslim every day." The Companions (may Allah be pleased with them) said: "What if he does not find (anything)?" He (peace and blessings be upon him) said: "Let him work with his hand, benefit himself and give charity." The Companions (may Allah be pleased with them) said: "What if he does not do so?" He (peace and blessings be upon him) said: "Let him help the distressed person in need." The Companions (may Allah be pleased with them) said: "What if he is not able to?" He (peace and blessings be upon him) said: "Let him enjoin good and forbid evil." The Companions (may Allah be pleased with them) said: "What if he is not able to?" He (peace and blessings be upon him) said: "Let him refrain from evil, for that is charity for him."
(b) These are the words of Abu Dawud's narration; Sulayman's narration does not have "every day", nor the words "and forbid evil".
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20207