The Prophet ﷺ said, "A person remains at ease in his religion as long as he does not shed unlawful blood."
حدثنا أبو النضر حدثنا إسحاق بن سعيد عن أبيه
عن النبي ﷺ أنه قال لن يزال المرء في فسحة من دينه ما لم يصب دما حراما
Its isnad is sahih. Bukhari related it in 12:165 from Ali bin Madini from Abu Nadr with this isnad. Hakim related it in Mustadrak 4:351 by way of Harith bin Abu Usama from Abu Nadr, with the same wording, and he graded it sahih. He also related it just before that, on page 350, by way of Darawardi from Ubaydullah bin Umar from Nafi from Ibn Umar, and he said, "Its isnad is sahih according to the criterion of the two Shaykhs, though they did not include it." Dhahabi agreed with him. It is strange that he did not add a note pointing out that Bukhari had in fact included it, perhaps he simply forgot.