Srimad Bhagavatam Canto 10, Chapter 04, Text 14

SB 10.4.14

tayabhihitam akarnya
 kamsah parama-vismitah
devakim vasudevam ca
 vimucya prasrito ’bravit
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
After hearing the words of the goddess Durga, Kamsa was struck with wonder. Thus he approached his sister Devaki and brother-in-law Vasudeva, released them immediately from their shackles, and very humbly spoke as follows.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Kamsa was astonished because the goddess Durga had become the daughter of Devaki. Since Devaki was a human being, how could the goddess Durga become her daughter? This was one cause of his astonishment. Also, how is it that the eighth child of Devaki was a female? This also astonished him. Asuras are generally devotees of mother Durga, Sakti, or of demigods, especially Lord Siva. The appearance of Durga in her original eight-armed feature, holding various weapons, immediately changed Kamsa’s mind about Devaki’s being an ordinary human. Devaki must have had some transcendental qualities; otherwise why would the goddess Durga have taken birth from her womb? Under the circumstances, Kamsa, struck with wonder, wanted to compensate for his atrocities against his sister Devaki.
Srimad Bhagavatam Canto 10, Chapter 04, Text 13
Srimad Bhagavatam Canto 10, Chapter 04, Text 15