śrī-śuka uvāca
svasur vadhān nivavṛte
kaṁsas tad-vākya-sāra-vit
vasudevo 'pi taṁ prītaḥ
praśasya prāviśad gṛham
śrī-śukaḥ uvāca - Śrī Śukadeva Gosvāmī said; svasuḥ - of his sister (Devakī); vadhāt - from the act of killing; nivavṛte - stopped for the time being; kaṁsaḥ - Kaṁsa; tat-vākya - the words of Vasudeva; sāra-vit - knowing to be perfectly correct; vasudevaḥ - Vasudeva; api - also; tam - to him (Kaṁsa); prītaḥ - being satisfied; praśasya - pacifying more; prāviśat gṛham - entered his own house.
Although Kaṁsa was a sinful demon, he believed that Vasudeva would never deviate from his word. The character of a pure devotee like Vasudeva is such that even so great a demon as Kaṁsa firmly believed in his words and was satisfied. Yasyāsti bhaktir bhagavaty akiñcanā sarvair guṇais tatra samāsate surāḥ (Bhāg. 5.18.12). All good attributes are present in a devotee, so much so that even Kaṁsa believed in Vasudeva’s words without a doubt.