Others say that since both Vasudeva and Devakī prayed for You, You have taken Your birth as their son. Undoubtedly You are unborn, yet You take Your birth for their welfare and to kill those who are envious of the demigods.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
अपरे वसुदेवस्य देवक्यां याचितोऽभ्यगात् । अजस्त्वमस्य क्षेमाय वधाय च सुरद्विषाम्
apare vasudevasya devakyāṃ yācito'bhyagāt | ajastvamasya kṣemāya vadhāya ca suradviṣām
SB 1.8.33