Srila A.C. Bhaktivedanta Swami Prabhupada. 26th March 1977. Room Conversation, Bombay.
The demons are very intelligent. He thought that “Round about way I shall become immortal.” He prayed to Brahmä that “Please give me the benediction that I shall not be killed by any man or any animal.” Brahmä said, “Yes, that is all right.” “I shall not be killed in the sky, on the water or on land.” Brahmä said, “Oh yes.” “I shall not be killed by any man-made weapons.” “That’s all right.” In this way he utilized his intelligence in so many ways just to come to the conclusion of being immortal. But the Lord is so cunning that He kept intact all the benediction given by Brahmä, still he was killed. He said that “I’ll not be killed either during daytime or night.” Brahmä said “Yes.” So he was killed just in the evening, just in the junction of day and night. You cannot say it is day or night. He took the benediction that “I shall not be killed in the sky, on the water, on the land.” So he was killed on His lap. He took the benediction that “I shall not be killed by any man-made or any God-made weapons.” That was given, “All right.” So he was killed by the nails. In this way, all the benedictions were kept intact, still he was killed. Similarly, we may make plan, we may make very advancement in scientific knowledge, but the killing process of nature will be there. Nobody can escape. By our intelligence we cannot escape. The four principles of material existence means birth, death, old age and disease. " (A.C. Bhaktivedanta Swami Prabhupada. 18th February 1970. Class on Sri Varaha-dwadasi purporting the Dasavatar-stotra - Ten main incarnations of the Lor. Los Angeles.)