Translation
(34) Sales and Trade
كتاب البيوع
(12) Chapter: Allah's Statement: "... Spend of the good things which you have earned ..."
(12) بَابُ قَوْلِ اللَّهِ تَعَالَى: {أَنْفِقُوا مِنْ طَيِّبَاتِ مَا كَسَبْتُمْ}
Sahih al-Bukhari 2066 

Narrated Abu Huraira:

The Prophet (ﷺ) said, "If a woman gives something (i.e. in charity) from her husband's earnings without his permission, she will get half his reward."

حَدَّثَنِي يَحْيَى بْنُ جَعْفَرٍ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، عَنْ مَعْمَرٍ، عَنْ هَمَّامٍ، قَالَ سَمِعْتُ أَبَا هُرَيْرَةَ ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏ "‏ إِذَا أَنْفَقَتِ الْمَرْأَةُ مِنْ كَسْبِ زَوْجِهَا عَنْ غَيْرِ أَمْرِهِ، فَلَهُ نِصْفُ أَجْرِهِ ‏"‏‏.‏
Reference : Sahih al-Bukhari 2066
In-book reference : Book 34, Hadith 19
USC-MSA web (English) reference : Vol. 3, Book 34, Hadith 280
  (deprecated numbering scheme)