Romans 14:5
One person regards a certain day more important than another; the next person regards every day alike. Each person should be fully convinced in his own mind [i.e., concerning their relative importance].
Romans 14:23
But the person who has doubts about eating [a certain food] is self-condemned if he [goes ahead and] eats it, because his action is not based on faith [i.e., if he lacks the conviction that he is doing what is right]. And whatever is not done with such a conviction is a sin.
Romans 14:14
As one who is in [fellowship with] the Lord Jesus, I am fully convinced that nothing in itself is [ceremonially] unclean. But to the person who considers something [ceremonially] unclean, it then becomes unclean to him.
1 Corinthians 8:7
However, not every person knows this [truth]. For some people have been so used to an idol all this time that they still think of the idol [as a reality] when eating food that has been sacrificed to it. And their weak conscience becomes polluted. [Note: These people cannot seem to shake off the idea that somehow the idol is real, so feel guilty of wrongdoing when eating food sacrificed to it].
1 Corinthians 8:11
So, this weak brother, for whose sake Christ died, becomes [spiritually] destroyed, [and all] because of your "knowledge" [i.e., you know that such eating is harmless, but your weak brother does not know this, so he is led into sin by your unloving example].
Galatians 4:9-10
But now that you have come to know God [as your Father], or rather, to be known by Him [as His children], how can you turn back again to the weak, cheap, elementary teachings [of the law of Moses], to which you [seem to] desire to become enslaved?
Colossians 2:16-17
So, do not allow anyone to judge [i.e., condemn] you for what you eat, or what you drink, or regarding [your non-observance of] a [yearly] festival, or a [monthly] "new moon" observance, or a [weekly] Sabbath day.
1 John 3:19-21
And this is how we will know that we are following [God's] truth, and will have assurance [of it] in our hearts and before God [as well].