The Statement of Allah "On the Day when that (Al-Kanz—money gold and silver, etc., the Zakät of which has not been paid) will be heated in the fire of Hell, and with it will be branded their foreheads…" (V.9:35)
Narrated Khãlid bin Aslam:We went out with 'Abdullãh bin 'Umar and he said, "This (Verse) was revealed before the prescription of Zakat, and when Zakãt was prescribed, Allah made it a means of purifying one's wealth."
Reference
Sahih al-Bukhari 4661
In-book reference
Book 65, Hadith 183
USC-MSA web (English)
Vol. 1, Book 60, Hadith 183
Translation by Dr. M. Muhsin Khan · Language: EN
Sahih
Arabic Text
وَقَالَ أَحْمَدُ بْنُ شَبِيبِ بْنِ سَعِيدٍ حَدَّثَنَا أَبِي، عَنْ يُونُسَ، عَنِ ابْنِ شِهَابٍ، عَنْ خَالِدِ بْنِ أَسْلَمَ، قَالَ خَرَجْنَا مَعَ عَبْدِ اللَّهِ بْنِ عُمَرَ فَقَالَ هَذَا قَبْلَ أَنْ تُنْزَلَ، الزَّكَاةُ، فَلَمَّا أُنْزِلَتْ جَعَلَهَا اللَّهُ طُهْرًا لِلأَمْوَالِ.