Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.084.

It is permissible for the person giving sadaqah to disclose his sadaqah, whether it is of an obligatory or supererogatory type (nafilah), so long as he does not do it ostentatiously. However, it is preferable not to disclose it. Allah, the Exalted One, says: “If you publicize your almsgiving, it is alright, but if you hide it and give it to the poor, it will be better for you” [al-Baqarah 271]. Ahmad, alBukhari, and Muslim relate from Abu Hurairah that the Prophet, upon whom be peace, said: “Seven people will be shaded by Allah on the day when there will be no shade except His. These people are: a just ruler, a young man who has been brought up in the worship of Allah, a man whose heart is attached to the mosque, two persons who love each other only for Allah’s sake and they meet and depart in Allah’s cause only, a person who gives sadaqah so secretly that his left hand does not know what his right hand has given, a person who remembers Allah in his seclusion and his eyes get filled with tears, and a man who refuses the call of a charming woman of noble birth for illicit sex and says: ‘I am afraid of Allah, the Exalted One.'”