كتاب المساقاة
22  
The Book of Musaqah
(22)
Chapter: It is permissible to lend animals and it is recommended to pay in full, giving something better than that which ts owed
(22)
باب مَنِ اسْتَسْلَفَ شَيْئًا فَقَضَى خَيْرًا مِنْهُ وَ ‏"‏ خَيْرُكُمْ أَحْسَنُكُمْ قَضَاءً ‏"‏ ‏‏
Sahih Muslim 1600 b

Abu Rafi', the freed slave of Allah's Messenger (ﷺ), said:

Allah's Messenger (ﷺ) took as a loan (the rest of the hadith is the same), but with this variation that he (the Holy Prophet) said: Good amongst the servants of Allah is he who is best in paying off the debt.
حَدَّثَنَا أَبُو كُرَيْبٍ، حَدَّثَنَا خَالِدُ بْنُ مَخْلَدٍ، عَنْ مُحَمَّدِ بْنِ جَعْفَرٍ، سَمِعْتُ زَيْدَ بْنَ أَسْلَمَ، أَخْبَرَنَا عَطَاءُ بْنُ يَسَارٍ، عَنْ أَبِي رَافِعٍ، مَوْلَى رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ اسْتَسْلَفَ رَسُولُ اللَّهِ صلى الله عليه وسلم بَكْرًا ‏.‏ بِمِثْلِهِ غَيْرَ أَنَّهُ قَالَ ‏ "‏ فَإِنَّ خَيْرَ عِبَادِ اللَّهِ أَحْسَنُهُمْ قَضَاءً ‏"‏ ‏.‏
Reference : Sahih Muslim 1600b
In-book reference : Book 22, Hadith 148
USC-MSA web (English) reference : Book 10, Hadith 3897
  (deprecated numbering scheme)