How does a person become free from sin?
See:
1 Jn 1:7 J. Vernon McGee
Response to comment [from a Christian]: "Does J. Vernon McGee believe that it is possible for a child of God to not walk in the light?"
Believers have yet the remains of sin in them (Ro 7:17,23; Ga 5:17).
Response to comment [from a Christian]: "We will be cleansed of all our sins..."
Justification is a one-time event (Isa 45:25; 53:11). Sanctification is an ongoing process (Heb 2:11; 13:12).
Response to comment [from a Christian]: "What about Hebrews 10:10...?"
We haven't arrived yet.
Heb 10:10 sanctified. “Sanctify” means to “make holy,” to be set apart from sin for God (cf. 1 Thess. 4:3). When Christ fulfilled the will of God, He provided for the believer a continuing, permanent condition of holiness (Eph. 4:24; 1 Thess. 3:13). This is the believer’s positional sanctification as opposed to the progressive sanctification that results from daily walking by the will of God (see notes on Rom. 6:19; 12:1,2; 2 Cor. 7:1).
Phil 3:12–14 Paul uses the analogy of a runner to describe the Christian’s spiritual growth. The believer has not reached his goal of Christlikeness (cf. vv. 20, 21), but like the runner in a race, he must continue to pursue it. That this is the goal for every believer is also clear from Rom. 8:29; 2 Thess. 2:14; 1 John 3:2 (see notes there).
"What instruction should we give someone, believer or unbeliever, about how to be free from sin?"
Got Jesus? Mt 6:33
[Ac 26:18]
"Ac 26:18 to open their eyes. Unbelievers are blinded to spiritual truth by Satan (2 Cor. 4:4; 6:14; cf. Matt. 15:14). from darkness to light. Since unbelievers are in the darkness of their spiritual blindness, the Bible often uses light to picture salvation (v. 23; 13:47; Matt. 4:16; John 1:4, 5, 7–9; 3:19–21; 8:12; 9:5; 12:36; 2 Cor. 4:4; 6:14; Eph. 5:8, 14; Col. 1:12, 13; 1 Thess. 5:5; 1 Pet. 2:9; 1 John 1:7; 2:8–10)."[1 Co 1:2]
You are simply in Christ.
That does not mean you are Christ.
"1 Co 1:2 saints. Not referring to a specially pious or revered
person canonized by an ecclesiastical body, but a reference to
everyone who by salvation has been sanctified, that is, set apart
from sin in Christ Jesus (cf. Gal. 1:6; Eph. 4:1, 4; Col. 3:15–17; 1
Tim. 6:12; Heb. 10:10, 14; 1 Pet. 2:9, 21; 3:9; 2 Pet. 1:3; Jude
1)." MacArthur, John Jr: The MacArthur Study Bible. electronic ed.
Nashville : Word Pub., 1997, c1997, S. 1 Co 1:2