two are the things which I remember Messenger of Allah ﷺ having said: "Verily Allah has enjoined excellence to everything; so when you kill, kill in a good way and when you slaughter, slaughter in a good way. So every one of you should sharpen his knife, and let the slaughtered animal die comfortably."  

ثِنْتَانِ حَفِظْتُهُمَا عَنْ رَسُولِ اللَّهِ ﷺ قَالَ: «إِنَّ اللَّهَ كَتَبَ الإِحْسَانَ عَلَى كُلِّ شَىْءٍ: فَإِذَا قَتَلْتُمْ فَأَحْسِنُوا الْقِتْلَةَ، وَإِذَا ذَبَحْتُمْ فَأَحْسِنُوا الذَّبْحَ، وَلْيُحِدَّ أَحَدُكُمْ شَفْرَتَهُ فَلْيُرِحْ ذَبِيحَتَهُ۔»