Emperor Constantine the Great issues a decree condemning those who harbor soothsayers, even the friends of soothsayers.
According to Constantine:
"Soothsayers, priests, and those who usually minister to such ceremonies are banned from approaching a private home even under the pretext of friendship.
Anyone who ignores this law will be punished, but if you think that soothsaying has advantages you are free to go to public altars and shrines to celebrate the rites of your custom. We do not prohibit any ceremonies of a bygone perversion to be conducted publicly." [CTh 9.16.2]
A soothsayer is someone who practices divination, meaning to predict the future or give advice based on signs from spirits or gods. This is contrary to the Christian worldview, according to which all such power must necessarily come from demons or Satan.
Emperor Constantine the Great had already suppressed some of the practices of magicians a few years earlier, and this is another step in the process of completely eliminating all spiritual and supernatural practices that might compete with or contradict Christian orthodoxy.