Abu Sa'id reported the Prophet (ﷺ) as saying, "The believer and faith are like a horse with the stake to which it is tethered, which moves round and then returns to its stake, for the believer is negligent and then returns to faith. Feed the pious with your food and confer your kindness on the believers." Baihaqi, in Shu'ab al-iman, and Abu Nu'aim, in al-Hilya, transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَنْ أَبِي سَعِيدٍ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «مَثَلُ الْمُؤْمِنِ وَمَثَلُ الْإِيمَانِ كَمَثَلِ الْفَرَسِ فِي آخِيَّتِهِ يَجُولُ ثُمَّ يَرْجِعُ إِلَى آخِيَّتِهِ وَإِنَّ الْمُؤْمِنَ يَسْهُو ثُمَّ يَرْجِعُ إِلَى الْإِيمَانِ فَأَطْعِمُوا طَعَامَكُمُ الْأَتْقِيَاءَ وَأَوْلُوا مَعْرُوفَكُمُ الْمُؤْمِنِينَ» . رَوَاهُ الْبَيْهَقِيُّ فِي «شُعَبِ الْإِيمَانِ» وَأَبُو نُعَيْمٍ فِي «الْحِلْية»
sunnah.com