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." (DE)
English reference (DE): Vol. 3, Book 21, Hadith 2619 (DE)
Arabic reference (DE): Book 21, Hadith 2717 (DE)