Backslider

Concise Bible Dictionary:

There are four Hebrew words applied to backsliding.
1. sug, “to go back”: “the backslider in heart shall be filled with his own ways,”‘ instead of God’s ways (Prov. 14:1414The backslider in heart shall be filled with his own ways: and a good man shall be satisfied from himself. (Proverbs 14:14)).
2. sarar, to act like a refractory heifer, that will not draw regularly in the plow: to which Israel is compared (Hos. 4:1616For Israel slideth back as a backsliding heifer: now the Lord will feed them as a lamb in a large place. (Hosea 4:16)).
3. meshubah, “a turning away, apostasy.” (Jer. 2:1919Thine own wickedness shall correct thee, and thy backslidings shall reprove thee: know therefore and see that it is an evil thing and bitter, that thou hast forsaken the Lord thy God, and that my fear is not in thee, saith the Lord God of hosts. (Jeremiah 2:19); Jer. 3:22, 6-1222Return, ye backsliding children, and I will heal your backslidings. Behold, we come unto thee; for thou art the Lord our God. (Jeremiah 3:22)
6The Lord said also unto me in the days of Josiah the king, Hast thou seen that which backsliding Israel hath done? she is gone up upon every high mountain and under every green tree, and there hath played the harlot. 7And I said after she had done all these things, Turn thou unto me. But she returned not. And her treacherous sister Judah saw it. 8And I saw, when for all the causes whereby backsliding Israel committed adultery I had put her away, and given her a bill of divorce; yet her treacherous sister Judah feared not, but went and played the harlot also. 9And it came to pass through the lightness of her whoredom, that she defiled the land, and committed adultery with stones and with stocks. 10And yet for all this her treacherous sister Judah hath not turned unto me with her whole heart, but feignedly, saith the Lord. 11And the Lord said unto me, The backsliding Israel hath justified herself more than treacherous Judah. 12Go and proclaim these words toward the north, and say, Return, thou backsliding Israel, saith the Lord; and I will not cause mine anger to fall upon you: for I am merciful, saith the Lord, and I will not keep anger for ever. (Jeremiah 3:6‑12)
; Jer. 5:66Wherefore a lion out of the forest shall slay them, and a wolf of the evenings shall spoil them, a leopard shall watch over their cities: every one that goeth out thence shall be torn in pieces: because their transgressions are many, and their backslidings are increased. (Jeremiah 5:6); Jer. 8:55Why then is this people of Jerusalem slidden back by a perpetual backsliding? they hold fast deceit, they refuse to return. (Jeremiah 8:5); Jer. 14:77O Lord, though our iniquities testify against us, do thou it for thy name's sake: for our backslidings are many; we have sinned against thee. (Jeremiah 14:7); Hos. 11:77And my people are bent to backsliding from me: though they called them to the most High, none at all would exalt him. (Hosea 11:7); Hos. 14:44I will heal their backsliding, I will love them freely: for mine anger is turned away from him. (Hosea 14:4)).

From Anstey’s Doctrinal Definitions:

The words “backsliding” and backslider are not found in the New Testament, but this kind of sad departure from God surely is mentioned (Mark 14:3030And Jesus saith unto him, Verily I say unto thee, That this day, even in this night, before the cock crow twice, thou shalt deny me thrice. (Mark 14:30); James 5:1919Brethren, if any of you do err from the truth, and one convert him; (James 5:19)). It has to do with a believer becoming careless in heart as to his communion with God (Prov. 14:1414The backslider in heart shall be filled with his own ways: and a good man shall be satisfied from himself. (Proverbs 14:14)), and if this is not judged, it will result in a wayward walk from the Lord. The work of Christ as an Advocate brings the backslider back. The restoration of the backslider involves repentance and the confession of sins to the Father (1 John 1:99If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness. (1 John 1:9)). (See Advocacy.)
•  We will lose spiritual energy.