Ecclesiastes 10:8 He that diggeth a pit shall fall into it; and whoso breaketh an hedge, a serpent shall bite him.

An hedge is a barrier to prevent access in other to protect or to prevent escape.

From the story of Job, God set an hedge around job.

Job 1:10 Hast not thou made an hedge about him, and about his house, and about all that he hath on every side? thou hast blessed the work of his hands, and his substance is increased in the land.

God's word can can serve as a barrier to prevent us from putting oursef in harms way when we think we know better, we more smarter or intelligent, or more educated we can end up breaking that hedge.

The result of breaking an hedge is that the serpent will bite.
The serpent is the devil, he is waiting to do as much damage as opportunity present itself.
As serpent are very quick and many of them has venom, so is Satan, he is fast in taking opportunity, and his venom are doubting God's word, fear, rebellion, amongst others.
The serpent introduces his venom and leaves waiting for the damage to be done.

Once a church gives Satan an opportunity he introduce his venom, and that venom began to work slowly in the heart of those in that church, it leads people to question God, not trust God and rebel against God.

There are many ministers of Satan running around with great charismatic and oratory coupled with false signs, their mission is to subtly, without being detected inject Satan's venom into the body of christ, they mix lies with truth, as Christians it is our duty to resist the devil and expose every works of darkness. While we ourselves should be careful of fallen into those same errors we are saving others from.