apare vasudevasya
devakyāṁ yācito 'bhyagāt
ajas tvam asya kṣemāya
vadhāya ca sura-dviṣām
apare - others; vasudevasya - of Vasudeva; devakyām - of Devakī; yācitaḥ - being prayed for; abhyagāt - took birth; ajaḥ - unborn; tvam - You are; asya - of him; kṣemāya - for the good; vadhāya - for the purpose of killing; ca - and; sura-dviṣām - of those who are envious of the demigods.
It is also said that Vasudeva and Devakī, in their previous birth as Sutapā and Pṛśni, underwent a severe type of penance to get the Lord as their son, and as a result of such austerities the Lord appeared as their son. It is already declared in the Bhagavad-gītā that the Lord appears for the welfare of all people of the world and to vanquish the asuras, or the materialistic atheists.