Ex 15:23-27 And when they came to Marah, they could not drink of the waters of Marah, for they were bitter: therefore the name of it was called Marah.

  And the people murmured against Moses, saying, What shall we drink?

  And he cried unto the LORD; and the LORD shewed him a tree, which when he had cast into the waters, the waters were made sweet: there he made for them a statute and an ordinance, and there he proved them,

  And said, If thou wilt diligently hearken to the voice of the LORD thy God, and wilt do that which is right in his sight, and wilt give ear to his commandments, and keep all his statutes, I will put none of these diseases upon thee, which I have brought upon the Egyptians: for I am the LORD that healeth thee.

  And they came to Elim, where were twelve wells of water, and threescore and ten palm trees: and they encamped there by the waters.

Bitter Waters.  I.e. Polluted water.

How does water become bitter?  By being mixed with harmful contents such as chemicals, urine, faeces, carcasses of dead animals.  What happens if people drink such water?  They become ill and can sometimes die.

Many serious diseases can be caught by drinking contaminated water;

Dysentery

Cryptosporidiosis (A diarrheal disease caused by a parasite that lives in human and animal intestines. The parasite can survive outside the body for a long time and resist chlorine disinfection. One mouthful of contaminated water can cause infection),

E coli 157:H7 (A strain of bacteria that causes severe diarrhea with bleeding and abdominal cramps. Primarily spread through uncooked meat, it can be contracted by swimming in contaminated water).

Giardiasis:  (A diarrheal illness caused by a parasite that lives in the intestines of people and animals. One of the most common causes of waterborne disease in the United States, it is contracted by mouth contact with feces-contaminated water).

Hepatitis A: (Caused by a virus, this disease may be spread by contact with water contaminated with human feces or by people who did not wash their hands properly. Symptoms include fever, loss of appetite and nausea, although children younger than 3 may not have symptoms but can still spread the virus).

Leptospirosis:  (A bacterial disease that could include high fever, severe headache, chills and vomiting. Untreated, it can cause kidney or liver damage, meningitis, and, in rare cases, death. Caused by exposure to water contaminated with the urine of infected animals).

Naegleria fowleri:  (An amoeba that causes primary amoebic meningoencephalitis, a rare disease that is almost always fatal. The amoeba, found normally in the sediment of many Florida lakes, becomes infectious at temperatures from 82 to 86 degrees and higher).

Shigellosis:  (A bacterial disease that causes diarrhoea, fever and stomach cramps and is spread by contact with fecal material).

Swimmer's itch:  (A skin rash caused by an allergic reaction to parasites found in birds and mammals that is spread by snails. The parasites are found in salt water and fresh water. Burning and itching symptoms may get worse with more exposure).

Viral gastroenteritis: (Watery diarrhoea and vomiting caused by a number of viruses, such as Norwalk virus. May be spread by swallowing water contaminated by infected individuals).

No one would dream of drinking polluted waters unless they were so desperate that that was all they had to drink, or an enemy had deliberately polluted the waters and mixed it with something that couldnt be detected.

Such is the situation in the churches today that Christians everywhere are drinking the Bitter waters of false teaching.  This is a deadly state of affairs.

Worse yet there are those that know that the waters are polluted but tell us that we can drink of the water, just, take out what is good and omit from ones mind that which isnt!  That is like saying,As there is pure water mixed with the contamination dont worry.  Your body will filter out that which is bad and so you wont be harmed!

Why drink polluted waters when we can have the pure unadulterated Word of God straight from the Bible?

What are we to do? (If thou wilt diligently hearken to the voice of the LORD thy God, and wilt do that which is right in his sight, and wilt give ear to his commandments, and keep all his statutes, I will put none of these diseases upon thee, which I have brought upon the Egyptians: for I am the LORD that healeth thee).