Matthew 15:6 (KJV) says:

Thus have ye made the commandment of God of none effect by your tradition.

Let's look at this in the Amplified Bible Classic Edition (AMPC).

So for the sake of your tradition (the rules handed down by your forefathers), you have set aside the Word of God [depriving it of force and authority and making it of no effect].

We must choose truth over tradition.  We must believe the truth or God's Word will do us no good.  There is so much man-made tradition and so many wrong ideas out there that can undermine our relationship with God.  For example, God's not mad at you; the cross proves that.  God is not out to get you, but instead He wants to save you.  Keep in mind that God is good and the devil is bad.  God wants to bless you.  The devil wants to steal from you.  It is always God's will to heal and prosper you.  The devil wants you to be sick and broke.

In John 10:10 (KJV), Jesus Himself says:

The thief cometh not, but for to steal, and to kill, and to destroy: I am come that they might have life, and that they might have it more abundantly.

John 10:10 in the Voice Translation (VOICE):

The thief approaches with malicious intent, looking to steal, slaughter, and destroy; I came to give life with joy and abundance.

Tradition will turn things around and will go against God's Word.  It is nothing but empty rules and regulations made up by men.  Jesus is the Truth (John 14:6), and His Word is true, meaning that if you know the Bible, you know the truth.  Truth that is known and acted upon releases God's power to meet your every need.

So, if someone tries to teach you something contrary to the Word, then it is likely man's tradition, and not truth.  Truth always lines up with the Word.  Choose truth and reject tradition.

Then you will know the truth, and the truth will set you free.  John 8:32 (NIV)