"Never will you attain the good [reward of righteousness] until you spend [in the way of Allah] from that which you love" (Quran 3:92). Al-Hasan said: He means the obligatory zakat. "And whatever you spend, indeed Allah is Knowing of it" (Quran 3:92). He preserves it for you until He recompenses you for it. [Verses 93-96]
﴿لَنْ تَنَالُوا الْبِرَّ حَتَّى تُنْفِقُوا مِمَّا تحبون﴾ قَالَ الْحسن: يَعْنِي الزَّكَاة (ل ٤٩) الْوَاجِبَة ﴿وَمَا تُنْفِقُوا مِنْ شَيْءٍ فَإِن الله بِهِ عليم﴾ يحفظه لكم حَتَّى يجازيكم بِهِ. [آيَة ٩٣ - ٩٦]