God gave these four young men an unusual aptitude for learning the literature and science of the time. And God gave Daniel special ability in understanding the meanings of visions and dreams.
When the three-year training period ordered by the king was completed, the chief official brought all the young men to King Nebuchadnezzar.
The king talked with each of them, and none of them impressed him as much as Daniel, Hananiah, Mishael, and Azariah. So they were appointed to his regular staff of advisers.
In all matters requiring wisdom and balanced judgment, the king found the advice of these young men to be ten times better than that of all the magicians and enchanters in his entire kingdom.
Daniel remained there until the first year of King Cyrus's reign.
References for Daniel 1:21