SB 10.2.20

tāṁ vīkṣya kaṁsaḥ prabhayājitāntarāṁ
 virocayantīṁ bhavanaṁ śuci-smitām
āhaiṣa me prāṇa-haro harir guhāṁ
 dhruvaṁ śrito yan na pureyam īdṛśī
Word for word: 
tām — her (Devakī); vīkṣya — after seeing; kaṁsaḥ — her brother Kaṁsa; prabhayā — with the enhancement of her beauty and influence; ajita-antarām — because of keeping Ajita, the Supreme Personality of Godhead, Viṣṇu, within herself; virocayantīm — illuminating; bhavanam — the whole atmosphere of the house; śuci-smitām — smiling and brilliant; āha — said to himself; eṣaḥ — this (Supreme Person); me — my; prāṇa-haraḥ — who will kill me; hariḥ — Lord Viṣṇu; guhām — within the womb of Devakī; dhruvam — certainly; śritaḥ — has taken shelter; yat — because; na — was not; purā — formerly; iyam — Devakī; īdṛśī — like this.
Translation: 
Because the Supreme Personality of Godhead was within her womb, Devakī illuminated the entire atmosphere in the place where she was confined. Seeing her jubilant, pure and smiling, Kaṁsa thought, “The Supreme Personality of Godhead, Viṣṇu, who is now within her, will kill me. Devakī has never before looked so brilliant and jubilant.”
Purport: 

The Lord says in Bhagavad-gītā (4.7):

yadā yadā hi dharmasya
 glānir bhavati bhārata
abhyutthānam adharmasya
 tadātmānaṁ sṛjāmy aham

“Whenever and wherever there is a decline in religious practice, O descendant of Bharata, and a predominant rise of irreligion — at that time I descend Myself.” In this age, at the present moment, there are inordinate discrepancies in the discharge of human duties. Human life is meant for God-realization, but unfortunately the materialistic civilization is stressing only the senses of the body, not understanding the living force within the body. As clearly stated in Bhagavad-gītā (dehino ’smin yathā dehe), within the body is the body’s proprietor, the living force, which is more important. But human society has become so fallen that instead of understanding the living force within the body, people have become busy with external things. This is a discrepancy in human duties. Therefore Kṛṣṇa has taken birth or taken shelter within the womb of the Kṛṣṇa consciousness movement. Men of Kaṁsa’s class, therefore, are very much afraid and are busy trying to stop this movement, especially in the Western countries. One politician has remarked that the Kṛṣṇa consciousness movement is spreading like an epidemic and that if not checked immediately, within ten years it may capture governmental power. There is, of course, such potency in the Kṛṣṇa consciousness movement. As stated by authorities (Cc. Ādi 17.22), kali-kāle nāma-rūpe kṛṣṇa-avatāra: in this age, Kṛṣṇa has appeared in the Hare Kṛṣṇa mahā-mantra. The Kṛṣṇa consciousness movement is spreading like wildfire all over the world, and it will go on doing so. Men who are like Kaṁsa are very much afraid of the movement’s progress and acceptance by the younger generation, but as Kṛṣṇa could not be killed by Kaṁsa, this movement cannot be checked by men of Kaṁsa’s class. The movement will go on increasing more and more, provided the leaders of the movement remain firmly Kṛṣṇa conscious by following the regulative principles and the primary activities of chanting the Hare Kṛṣṇa mantra regularly.