This excerpt is taken from Sheikh Abu Hamza Abdul Khaliq Siddiqi's book Sahih Fazail-e-Amaal.
Allah Almighty has said:
﴿الَّذِينَ يُنفِقُونَ أَمْوَالَهُم بِاللَّيْلِ وَالنَّهَارِ سِرًّا وَعَلَانِيَةً فَلَهُمْ أَجْرُهُمْ عِندَ رَبِّهِمْ وَلَا خَوْفٌ عَلَيْهِمْ وَلَا هُمْ يَحْزَنُونَ﴾
"Those who spend their wealth by night and by day, secretly and publicly, have their reward with their Lord. And no fear will there be concerning them, nor will they grieve."
Reference: (2-Al-Baqarah:274)
He further said:
﴿إِن تُبْدُوا الصَّدَقَاتِ فَنِعِمَّا هِيَ ۖ وَإِن تُخْفُوهَا وَتُؤْتُوهَا الْفُقَرَاءَ فَهُوَ خَيْرٌ لَّكُمْ ۚ وَيُكَفِّرُ عَنكُم مِّن سَيِّئَاتِكُمْ ۗ وَاللَّهُ بِمَا تَعْمَلُونَ خَبِيرٌ﴾
"If you disclose your charity, it is well and 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 [thereby]. And Allah is [fully] acquainted with what you do."
Reference: (2-Al-Baqarah:271)
(The above verse) indicates that concealing charity is preferable so that there is no suspicion of showing off. However, if there is a religious benefit in making it public, such as the intention that others may follow in the good deed, then making it public is better. Therefore, the majority of commentators hold the view that the preference for concealment is specific to voluntary charity. In obligatory charity and Zakat, making it public is preferable.
Reference: (Tayseer al-Rahman, 1/100-156)
Sayyiduna Abu Hurairah (may Allah be pleased with him) narrated that he heard the Messenger of Allah (peace be upon him) say: Allah will grant His shade to seven types of people on the Day when there will be no shade except His. One of them is a person who gives charity so secretly that his left hand does not know what his right hand has spent."
Reference: Sahih Bukhari, Book of Faith, No: 660 - Sahih Muslim, Book of Zakat, No: 1031
