Kamsa was astonished. 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

Expressions researched:
"Since Devakī was a human being, how could the goddess Durgā become her daughter? This was one cause of his astonishment. Also, how is it that the eighth child of Devakī was a female? This also astonished him" |"Kaṁsa was astonished because"

Srimad-Bhagavatam

SB Canto 10.1 to 10.13

Kaṁsa was astonished because the goddess Durgā had become the daughter of Devakī. Since Devakī was a human being, how could the goddess Durgā become her daughter? This was one cause of his astonishment. Also, how is it that the eighth child of Devakī was a female? This also astonished him. Asuras are generally devotees of mother Durgā, Śakti, or of demigods, especially Lord Śiva.

SB 10.4.14, Translation and Purport

After hearing the words of the goddess Durgā, Kaṁsa was struck with wonder. Thus he approached his sister Devakī and brother-in-law Vasudeva, released them immediately from their shackles, and very humbly spoke as follows.

Kaṁsa was astonished because the goddess Durgā had become the daughter of Devakī. Since Devakī was a human being, how could the goddess Durgā become her daughter? This was one cause of his astonishment. Also, how is it that the eighth child of Devakī was a female? This also astonished him. Asuras are generally devotees of mother Durgā, Śakti, or of demigods, especially Lord Śiva. The appearance of Durgā in her original eight-armed feature, holding various weapons, immediately changed Kaṁsa's mind about Devakī's being an ordinary human. Devakī must have had some transcendental qualities; otherwise why would the goddess Durgā have taken birth from her womb? Under the circumstances, Kaṁsa, struck with wonder, wanted to compensate for his atrocities against his sister Devakī.