From the christian scriptures especially 1. Thess 5:21 comes to mind. It says: "Prove all things; hold fast that which is good."
The latter part of that verse is often de-emphasized by cults who may tell you to "prove all things", but then begin interpreting the Bible for you. When people then have doubts that would normally lead them to look elsewhere for an answer so they could indeed "hold fast that which is good", they are told to rely upon a ministry - which then leads them astray further into error. They try proving all things, but end up more confused than ever before. Read my hub "Are you in a cult?" for more on this topic.
My favorite scripture is Deuteronomy 30:15-20 which says:
"See, I have set before thee this day life and good, and death and evil;
In that I command thee this day to love the LORD thy God, to walk in his ways, and to keep his commandments and his statutes and his judgments, that thou mayest live and multiply: and the LORD thy God shall bless thee in the land whither thou goest to possess it.
But if thine heart turn away, so that thou wilt not hear, but shalt be drawn away, and worship other gods, and serve them;
I denounce unto you this day, that ye shall surely perish, [and that] ye shall not prolong [your] days upon the land, whither thou passest over Jordan to go to possess it.
I call heaven and earth to record this day against you, [that] I have set before you life and death, blessing and cursing: therefore choose life, that both thou and thy seed may live:
That thou mayest love the LORD thy God, [and] that thou mayest obey his voice, and that thou mayest cleave unto him: for he [is] thy life, and the length of thy days: that thou mayest dwell in the land which the LORD sware unto thy fathers, to Abraham, to Isaac, and to Jacob, to give them."
A very encouraging message to ALL believers who rely upon God rather than man for real understanding in true respect for His Law (Psa. 111:10).