Sahih al-Bukhari 6690
Sahih al-Bukhari · Book 83: Oaths and Vows · If a person gives his property in charity because of a vow and as an expiation for sins
Narrated Ka`b bin Malik:
حَدَّثَنَا أَحْمَدُ بْنُ صَالِحٍ ، حَدَّثَنَا ابْنُ وَهْبٍ ، أَخْبَرَنِي يُونُسُ ، عَنِ ابْنِ شِهَابٍ ، أَخْبَرَنِي عَبْدُ الرَّحْمَنِ، عَنْ عَبْدِ اللَّهِ بْنِ كَعْبِ بْنِ مَالِكٍ ، وَكَانَ، قَائِدَ كَعْبٍ مِنْ بَنِيهِ حِينَ عَمِيَ ـ قَالَ سَمِعْتُ كَعْبَ بْنَ مَالِكٍ ، فِي حَدِيثِهِ {َعَلَى الثَّلاَثَةِ الَّذِينَ خُلِّفُوا} َقَالَ فِي آخِرِ حَدِيثِهِ إِنَّ مِنْ تَوْبَتِي أَنِّي أَنْخَلِعُ مِنْ مَالِي صَدَقَةً إِلَى اللَّهِ وَرَسُولِهِ. فَقَالَ النَّبِيُّ صلى الله عليه وسلم " أَمْسِكْ عَلَيْكَ بَعْضَ مَالِكَ فَهْوَ خَيْرٌ لَكَ " .
In the last part of his narration about the three who remained behind (from the battle of Tabuk). (I said) "As a proof of my true repentance (for not joining the Holy battle of Tabuk), I shall give up all my property for the sake of Allah and His Apostle (as an expiation for that sin)." The Prophet (ﷺ) said (to me), "Keep some of your wealth, for that is better for you."