Muslim Manners

Abu Musa Al-Ash’ari (may Allah be pleased with him) reported:

The Prophet Muhammad (may Allah’s peace be upon him) said:

“Giving in charity is an obligation upon every Muslim”. It was said (to him): “What about one who does not find (the means) to do so?”  He (may Allah’s peace be upon him) said, “Let him work with his hands, thus doing benefit to himself and give in charity.”  It was said to him: “What if he does not have (the means) to do so?”  He (may Allah’s peace be upon him) said, “Then let him assist the needy, the aggrieved.”  It was said: “What about if he cannot even do this?”  He (may Allah’s peace be upon him) said, “Then he should enjoin good.”  He was asked: “What if he cannot do that?”  He (the Prophet; may Allah’s peace be upon him) said, “He should then abstain from evil, for verily, that is a charity from him”.

[Al-Bukhari and Muslim]

Taken from:
http://www.alssunnahnet.com/en/articles.aspx?article_no=2749