The advice to take care of non-Muslims who have a covenant of Allah's Messenger saws Sahih al-Bukhari 3162
Arabic hadith text
حَدَّثَنَا آدَمُ بْنُ أَبِي إِيَاسٍ، حَدَّثَنَا شُعْبَةُ، حَدَّثَنَا أَبُو جَمْرَةَ، قَالَ سَمِعْتُ جُوَيْرِيَةَ بْنَ قُدَامَةَ التَّمِيمِيَّ، قَالَ سَمِعْتُ عُمَرَ بْنَ الْخَطَّابِ ـ رضى الله عنه ـ قُلْنَا أَوْصِنَا يَا أَمِيرَ الْمُؤْمِنِينَ. قَالَأُوصِيكُمْ بِذِمَّةِ اللَّهِ، فَإِنَّهُ ذِمَّةُ نَبِيِّكُمْ، وَرِزْقُ عِيَالِكُمْ.
Translation
Narrated Juwairiya bin Qudama at-Tamimi
We said to `Umar bin Al-Khattab, Jo Chief of the believers! Advise us." He said, "I advise you to fulfill Allah's Convention (made with the Dhimmis) as it is the convention of your Prophet and the source of the livelihood of your dependents (i.e. the taxes from the Dhimmis.) "