Bukhari

And Allah the Exalted said (in Surah Al-Baqarah) «الذين ينفقون أموالهم بالليل والنهار سرا وعلانية‏» "Those who spend their wealth by night and by day, secretly and openly, they shall have their reward with their Lord; on them shall be no fear, nor shall they grieve."

And Abu Huraira, may Allah be pleased with him, narrated from the Prophet, peace and blessings be upon him, that: "A man gave charity and concealed it so much that his left hand did not know what his right hand had spent." And Allah the Exalted has said: "If you disclose your charity, it is good, but if you conceal it and give it to the poor, it is better for you, and He will remove from you some of your misdeeds. And Allah is fully aware of what you do."

Narrated Abu Huraira: Allah's Apostle (p.b.u.h) said, "A man said that he would give something in charity. He went out with his object of charity and unknowingly gave it to a thief. Next morning the people said that he had given his object of charity to a thief. (On hearing that) he said, "O Allah! All the praises are for you. I will give alms again." And so he again went out with his alms and (unknowingly) gave it to an adulteress. Next morning the people said that he had given his alms to an adulteress last night. The man said, "O Allah! All the praises are for you. (I gave my alms) to an adulteress. I will give alms again." So he went out with his alms again and (unknowingly) gave it to a rich person. (The people) next morning said that he had given his alms to a wealthy person. He said, "O Allah! All the praises are for you. (I had given alms) to a thief, to an adulteress and to a wealthy man." Then someone came and said to him, "The alms which you gave to the thief, might make him abstain from stealing, and that given to the adulteress might make her abstain from illegal sexual intercourse (adultery), and that given to the wealthy man might make him take a lesson from it and spend his wealth which Allah has given him, in Allah's cause."