Yes, Christians do sin; please allow me to explain.

When an individual sincerely repents of their sin and with a sincere heart believes that Jesus Christ is Lord and that Jesus died for them on the Cross at Golgotha to pay their sin-debt, a debt owed the Father that they could never pay themselves, that individual is instantaneously made “positionally right” with the Father; what does this mean?

When one enters into covenant relationship with the Father by faith in the Son, Jesus Christ, they receive the IMPUTATION of Jesus' perfection-righteousness (the gift of Jesus’ sinless perfection) into and over their life, forever (John 3; 2 Corinthians 5:21). In addition, the one redeemed (purchased at a price) by faith in Jesus also receives the Gift of the indwelling Holy Spirit who is the Guarantor of covenant relationship with the Father, forever (Ephesians 1:13-14); in addition, the redeemed in Jesus also receive a ”new-nature” that wars against the old sin-nature received from our father, Adam (2 Corinthians 5:17; Romans 5:12) and a struggle between the two-natures ensues (Ephesians 4:22-32).

At this juncture, it is very important to understand a most relevant truism; sinful human kind can find righteousness (a right standing) with the Father ONLY by trusting in the Son, Jesus Christ, and receiving the righteousness, sinless purity, of the Son imputed into our life by faith and it is only by the imputation of Messiah’s perfection that the Father agrees, by covenant promise (Hebrews 8:12), to NOT see our sin by “choice” and the Father then declares the redeemed in Jesus “not guilty” of past-present-future sins.

The Father’s volitional decision-choice to forgive our sins is NOT based upon our worthiness before or subsequent covenant relationship but the Father’s “choice” to forgive our sin is based solely upon what His Son did for us on the Cross by fulfilling the mandates of Leviticus 17:11 relevant to blood atonement for sin (John 3:16).

Therefore, do not walk in the prevailing deception believing that once redeemed by faith in Jesus, having been declared “positionally right” with the Father by faith; having received the indwelling Holy Spirit; having received a new-nature that naturally loves God and wants to please Him as an obedient child, that you are sinless in reality as you remain encumbered by a body of decaying flesh that is stained and dying in sin (Romans 3:23; Romans 7:14-25).

Jesus, in the New Covenant, enhanced personal culpability concerning the law by the inclusion of mens rea or the “guilty mind” or the “thought life;” in other words, no longer would a man or woman be required to actually physiologically commit an offense toward the Father to be culpable for sin but Jesus taught that the mere “thoughts” of mankind are subject to judgment (Matthew 5:21-27); therefore, the Christian who remains in this World encumbered by a body of decaying flesh and sin does NOT walk in perfect righteousness with consistency but the Christian does sin in word, thought, deed, from time to time; therefore, we have an Advocate with the Father, Jesus Christ, and the Holy Spirit, who sustain us, make intercession for us, while the Father “chooses” to not see our sin as the Father only sees the perfection, the righteousness, of His dear Son in us; this is grace and mercy beyond human comprehension.

The Apostle John via the Holy Spirit tells the Christian that if we sin He, the Father, is faithful and just to forgive us of our sin and cleanse us from all unrighteousness (1 John 1:9)…why?

First of all, the Father would ask, “What sin?” as He has affirmatively made the divine “choice” to not see our sin, but 1 John 1:9 is not relevant to our covenant relationship with the Father, 1 John 1:9 is relevant for the Christian who sins and the benefits of the promise are for "conscience sake" not righteousness sake; that is, there is no greater GIFT than the peace and assurance provided by the indwelling Holy Spirit to the one redeemed by faith in Jesus (Romans 5:1) and when our sin-nature results in a temporary compromise with the World, the Spirit convicts the conscience and draws us back into obedience through a momentary loss of peace and intimacy with the Father; therefore, we apologize to our Father as a loving child NOT to reestablish covenant relationship as that is secure, forever, through the Spirit (Ephesians 1:13-14) but we apologize to reestablish INTIMACY and well-being with our Heavenly Father as life void that intimacy is simply not worth enduring.

Some may ask, is the Father’s grace and mercy relevant to sin in the life of a Christian a license for the Christian to sin and compromise with the World void conscience? Absolutely NOT! It is the Holy Spirit walking the redeemed in Jesus in the process of sanctification that methodically guides them, teaches them, in the Father's will and this is accomplished through the conscience (1 John 2:27; Galatians 5:16); therefore, anyone who names the Name of Jesus Christ as their Lord and walks in compromise with the World and in its defilement void conscience this person is spiritually deceived and the Spirit does not indwell them; therefore, they remain in their sin.

Jesus clearly said that you can recognize the Father’s children from the World by what they do, by their affections and their loyalties i.e., their “fruit” (Matthew 7:15-20). Though sin always crouches at the door of the Christian's life in Time, they are victorious because of the Father's grace, the Son's faithfulness, the Spirit's sanctification because greater is He that is in the Christian than He that controls the World's affections (1 John 4:4).