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Abu Huraira reported God’s messenger as saying, “When a woman gives something her husband has earned without being commanded by him to do so, she has half his reward.” (Bukhari and Muslim.)
Source: sunnah.com
Other translations
Arabic
وَعَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «إِذَا أَنْفَقَتِ الْمَرْأَةُ مِنْ كَسْبِ زَوْجِهَا مِنْ غَيْرِ أَمْرِهِ فَلَهَا نِصْفُ أَجْرِهِ»
sunnah.com