Histories

For these reasons they summoned him and tried to make him a friend, having bound him by tokens of good faith and oaths to keep to himself and betray to no one their deception of the Persians, and promising to give him all things in great abundance.

When Prexaspes agreed to do this, since the Magi importuned him, the Magi made this second proposal to him, that they should call an assembly of all the Persians before the palace wall, and he should go up on to a tower and declare that it was Smerdis son of Cyrus and no other who was king of Iran [53,32] (nation), AsiaPersia.

They gave him this charge, because they thought him to be the man most trusted by the Persians, and because he had often asserted that Cyrus' son Smerdis was alive, and had denied the murder.