Because she (Devaki) was now married to Vasudeva, she was para-stri, another man's wife, and if such a woman were killed, not only would Kamsa be implicated in sinful activities, but his reputation as king of the Bhoja dynasty would be damaged

Expressions researched:
"Because she was now married to Vasudeva, she was para-strī, another man's wife, and if such a woman were killed, not only would Kaṁsa be implicated in sinful activities, but his reputation as king of the Bhoja dynasty would be damaged"

Srimad-Bhagavatam

SB Canto 10.1 to 10.13

Because she was now married to Vasudeva, she was para-strī, another man's wife, and if such a woman were killed, not only would Kaṁsa be implicated in sinful activities, but his reputation as king of the Bhoja dynasty would be damaged. Thus Vasudeva tried in many ways to convince Kaṁsa in order to stop him from killing Devakī.

SB 10.1.37, Translation and Purport

Vasudeva said: My dear brother-in-law Kaṁsa, you are the pride of your family, the Bhoja dynasty, and great heroes praise your qualities. How could such a qualified person as you kill a woman, your own sister, especially on the occasion of her marriage?

According to Vedic principles, a brāhmaṇa, an old man, a woman, a child or a cow cannot be killed under any circumstances. Vasudeva stressed that Devakī was not only a woman but a member of Kaṁsa s family. Because she was now married to Vasudeva, she was para-strī, another man's wife, and if such a woman were killed, not only would Kaṁsa be implicated in sinful activities, but his reputation as king of the Bhoja dynasty would be damaged. Thus Vasudeva tried in many ways to convince Kaṁsa in order to stop him from killing Devakī.