Intro

A soothsayer is mostly in the old testament. Its not a saint. It seems that a good way to identify a soothsayer is to read about Balaam.

Bible verses

(Isaiah 30:10)
“Which say to the seers, See not; and to the prophets, Prophesy not unto us right things, speak unto us smooth things, prophesy deceits:”

A soothsayer might be connected to someone who speaks smooth things and prophecy deceits.

(Joshua 13:22 [KJV]) 
Balaam also the son of Beor, the soothsayer, did the children of Israel slay with the sword among them that were slain by them.

The soothsayer was slain by Gods people.

(Isaiah 2:6 [KJV]) 
Therefore thou hast forsaken thy people the house of Jacob, because they be replenished from the east, and are soothsayers like the Philistines, and they please themselves in the children of strangers.

The soothsayer is like a Philistine, that is like a lost person.

(Daniel 2:27 [KJV]) Daniel answered in the presence of the king, and said, The secret which the king hath demanded cannot' the wise men, the astrologers, the magicians, the soothsayers, shew unto the king;

The soothsayer cannot understand dreams because they don't have the holy ghost.

(Micah 5:12 [KJV]) And I will cut off witchcrafts out of thine hand; and thou shalt have no more soothsayers:

The soothsayer seems to be similar to witchcraft.

(Revelation of John 2:14 [KJV]) But I have a few things against thee, because thou hast there them that hold the doctrine of Balaam, who taught Balac to cast a stumblingblock before the children of Israel, to eat things sacrificed unto idols, and to commit fornication.

A soothsayer seems to be someone that puts stumblingblocks before the saints trying to get them to sin.

(II Peter 2:15 [KJV]) Which have forsaken the right way, and are gone astray, following the way of Balaam the son of Bosor, who loved the wages of unrighteousness;

Balaam the soothsayer loved the wages of unrighteousness.

(Nehemiah 13:2 [KJV]) Because they met not the children of Israel with bread and with water, but hired Balaam against them, that he should curse them: howbeit our God turned the curse into a blessing.

Balaam the soothsayer was hired to curse the Israelites.

Gods advice regarding Acts7brothers

Don't listen to what they have to say.