Be watchful, and strengthen the things which remain, that are ready to die, for I have not found your works perfect before God. I know your works, that you are neither cold nor hot. I could wish you were cold or hot. So then, because you are lukewarm, and neither cold nor hot, I will vomit you out of my mouth. (Revelation 3:2,15,16)

I have this against you, that you have left your first love. (Revelation 2:4)

If we confess ours sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness. (1 John 1:9)

Take heed to yourself, and diligently keep yourself, lest you forget the things your eyes have seen, and lest they depart from your heart all the days of your life. And teach them to your children and your grandchildren. (Deuteronomy 4:9)

Beware that you do not forget the Lord your God by not keeping His commandments, His judgments, and His statutes which I command you today, lest when you have eaten and are full, and have built beautiful houses and dwell in them; and when your herds and your flocks multiply, and your silver and your gold are multiplied, and all that you have is multiplied, when your heart is lifted up, and you forget the Lord your God who brought you out of the land of Egypt, from the house of bondage. (Deuteronomy 8:11-14)

If we had forgotten the name of our God, or stretched out our hands to a foreign god, would not God search this out? For He knows the secrets of the heart. (Psalm 44:20,21)

Beware, brethren, lest there be in any of you an evil heart of unbelief in departing from the living God; but exhort one another daily, while it is called "Today" lest any of you be hardened through the deceitfulness of sin. (Hebrews 3:12,13)

Of whom we have much to say, and hard to explain, since you have become dull of hearing. For though by this time you ought to be teachers, you need someone to teach you again the first principles of the oracles of God; and you have come to need milk and not solid food. (Hebrews 5:11,12)

"Yet from the days of your fathers you have gone away from My ordinances and have not kept them. Return to Me, and I will return to you." ..says the Lord of hosts. (Malachi 3:7)

If, after they have escaped the pollutions of this world through the knowledge of the Lord and Savior Jesus Christ, they have are again entangled in them and overcome, the latter end is worse for them than the beginning. For it would have been better for them not to have known the way of righteousness, than having known it, to turn from the holy commandment delivered to them. (2 Peter 2:20,21)