Islam Guidance

One day a Jewish person came to Imam Ali (A.S). He was planning to ask Imam Ali (A.S) such a question, which would take Imam Ali (A.S) a long time to answer and because of that his noon Prayers would be delayed.
He asked, "Imam Ali you say you know everything in the world, then tell me which animals lay eggs and which animals give birth to their young ones."
Imam Ali (A.S) looked back at him smiled and said, "The animals that have their 'EARS' outside their body give birth to their young ones and the animals that have their 'EARS' inside their body lay eggs."

Ref: Shia.es

So we sealed their ears [with sleep] in the cave for a number of years.
(Qur'an, 18:11)
The original Arabic of the phrase "We sealed their ears" in the Qur'an is the verb “daraba”. This bears the metaphorical meaning of "We have made them sleep." Used in reference to the ears, “daraba” means "preventing the ears from hearing." The fact that only the sense of hearing is mentioned here is very significant.
According to recent scientific discoveries, the ear is the only sensory organ active while a person is sleeping. This is why we need an alarm clock to wake up (Kazi, 130 Evident Miracles in the Quran, 108). The wisdom of the phrase "We sealed their ears" is, in all probability, that Allah closed the hearing of the young people in question, for which reason they remained asleep for many years.

Ref: The scientific miracles of the Quran