It was narrated from Bara' bin Azib that the Messenger of Allah (ﷺ) said:
"If this world were to be destroyed, that would be less significant before Allah (SWT) than the unlawful killing of a believer." (IT)
English reference (IT): Vol. 3, Book 21, Hadith 2619 (IT)
Arabic reference (IT): Book 21, Hadith 2717 (IT)