Matthew 17:3

And behold, there appeared unto them Moses and Elijah talking with him.

How did the apostles recognize Moses and Elijah? The conversation seems to be the most logical source of that information. It may be concluded from this incident that the saints will know the redeemed of all ages in their glorified state in heaven. The appearance of Moses and Elijah with Christ was strong proof of his deity, since Christ was able to recall from the hosts of righteous dead those typical representatives of previous dispensations. Moses the great lawgiver, and Elijah the great prophet, were there summoned from the dead to resign their commissions and to lay their homage at his feet. Then the apostles KNEW that Christ was not merely some great Elijah or other notable, and they were certain beyond all doubt that he was the One greater than all others, superior even to Moses and Elijah.