كتاب الزكاة
12  
The Book of Zakat
(14)
Chapter: The virtue of spending and giving charity to relatives, spuses, children and parents, even if they are idolaters
(14)
باب فَضْلِ النَّفَقَةِ وَالصَّدَقَةِ عَلَى الْأَقْرَبِينَ وَالزَّوْجِ وَالْأَوْلَادِ وَالْوَالِدَيْنِ وَلَوْ كَانُوا مُشْرِكِينَ
Sahih Muslim 1003 a

Asma' daughter of Abu Bakr reported:

I said: Messenger of Allah, my mother, who is inclined or scared has come to me. Should I (even An her position of being opposed to Islam) treat her well? He said: Yes.
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ إِدْرِيسَ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنْ أَسْمَاءَ، قَالَتْ قُلْتُ يَا رَسُولَ اللَّهِ إِنَّ أُمِّي قَدِمَتْ عَلَىَّ وَهْىَ رَاغِبَةٌ - أَوْ رَاهِبَةٌ - أَفَأَصِلُهَا قَالَ ‏ "‏ نَعَمْ ‏"‏ ‏.‏
Reference : Sahih Muslim 1003a
In-book reference : Book 12, Hadith 61
USC-MSA web (English) reference : Book 5, Hadith 2194
  (deprecated numbering scheme)