This idea of 'false brethren unawares brought in' was a warning which Paul gave also in

 

Acts 20: Read All.

2 Cor.11: Read all.

 

This is not a subject to consider lightly, because a little 'leaven' (false doctrine, a poison against Christ) affects the whole loaf. Christ also warned Christians about these false brethren who creep in;

 

 Matt.16:6; Then Jesus said unto them, “Take heed and beware of the leaven of the Pharisees, and of the Sadducees.

 

Mark 8:15; And he charged them, saying,” Take heed, beware of the leaven of the Pharisees, and of the leaven of Herod.

 

Luke 12:1; In the mean time, when there were gathered together an innumerable multitude of people, insomuch that they trode one upon another, He began to say unto His disciples first of all, “ Beware ye of the leaven of the Pharisees, which is hypocrisy.

     This phrase 'to spy out' in verse 4, which these 'false brethren' were doing, is 'kataskopeo' in the Greek meaning 'to be sentinel, i.e. to inspect insidiously' (Strong's no.2684). Reason with me for a moment.  Just how would these 'false brethren', who were pushing the Law of blood circumcision on the Gentiles, know whether one was circumcised or not? Well, they must have gone secretly peeking around the corner to discover that.
     Here's the gist of the Message. Who is given control by God over this earth flesh age and its kingdoms? Satan is.

 

 Luke 4:5-6: Read All.

 

 How do Satan's little 'workers of iniquity' operate in the world?  Behind the scenes initially, and always in secret; This is why many can't understand how all the evil can exist around us, even in a free Nation founded upon a trust in God, and abundant in His blessings.

Christ would teach...

 In Luke 8 & 11(Read all)

 ...That a true servant of The Lord does not put a candle (works in The Holy Spirit) under a bed, but on a table so it can give light to the whole room (world). Christ's own don't go around accomplishing their works in secret. But Satan's children do everything under a cloak of 'darkness', lest they be found out, and God's People punish them according to God's Commandments which were not done away with on the cross. God gives to His servants power over all His enemies;

 

Luke 10:19. Behold, I give unto you power to tread on serpents and scorpions, and over all the power of the enemy: and nothing by any means shall hurt you.

 

So Satan's own, for reasons of self-preservation, must do their dirty work in hiding, in secret, and they spy out in secret. There is no 'light' of The Holy Spirit in them. When Christ said in Matthew 10 that "...there is nothing covered, that shall not be revealed; and hid, that shall not be known.", He was referring to the time of His second Advent to earth, when all the evil works by those who follow Satan, will be exposed by Him, and Christ will be 'very accurate' in punishment.

 

 1 Cor.4:5: Therefore judge nothing before the time, until the Lord come.