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Surah 2. Al-Baqara
Ayah 270 - 271
270وَمَآ أَنفَقْتُم مِّن نَّفَقَةٍ أَوْ نَذَرْتُم مِّن نَّذْرٍ فَإِنَّ ٱللَّهَ يَعْلَمُهُۥ ۗ وَمَا لِلظَّـٰلِمِينَ مِنْ أَنصَارٍ
271إِن تُبْدُوا۟ ٱلصَّدَقَـٰتِ فَنِعِمَّا هِىَ ۖ وَإِن تُخْفُوهَا وَتُؤْتُوهَا ٱلْفُقَرَآءَ فَهُوَ خَيْرٌ لَّكُمْ ۚ وَيُكَفِّرُ عَنكُم مِّن سَيِّـَٔاتِكُمْ ۗ وَٱللَّهُ بِمَا تَعْمَلُونَ خَبِيرٌ
[270-271] Surely Allah knows whatever you may have spent and whatever vow you may have made, and the wrong-doers (who spend in the way of Satan) shall have no helpers.310 If you practise charity publicly, it is good; but if you give charity secretly to the needy, it is much better for you,311 for this will expiate many of your sins.312 Anyhow, Allah is well aware of whatever you do.
310Allah is fully aware of the intentions and actions of everyone and knows whether one spends in the way of Allah or in the way of Satan and whether .me makes a vow to Allah or to someone else. Therefore those, who spend fur His cause and make vows to Hint, will most surely get their rewards from Him. And those evildoers, who speed for the cause of Satan and make vows to others, shall have no helper to protect them from His punishment.
Nadhar (a vow) is a solemn pomise made by a person to perform some act, or make some offering or gift etc., not binding on him, in case some wish of his should be fulfilled. If that wish is lawful and is asked of Allah and the vow is made to Allah alone, such a vow must be fulfilled as a religious duty. for it is in obedience to Allah. But if the wish is unlawful or the vow is made to someone other than Allah, then the making of the vow is sinful and its fulfilment would merit condemnation.
311It is better to practise the obligatory charity (Zakat) openly and every other kind of charity secretly. The same principle applies to all other religious practices. It is better to perform the obligatory duties openly and the voluntary ones secretly.
312It helps reform the character of a man if he performs good deeds secretly. It develops virtues in him and eradicates vices. As a result, one becomes such a favourite of Allah, that Allah in view of one's virtue and sincerity, forgives any minor sins of commission or omission He wills.