Question: "Is entire sanctification / sinless perfection possible in this life?"
Answer: Ephesians 4:13 says that the spiritual gifts are given to build up the body of Christ “until we all reach unity in the faith and in the knowledge of the Son of God and become mature, attaining to the whole measure of the fullness of Christ.” Some translations say that we will become “perfect” (instead of “mature”), and from this some people have mistakenly thought that we can reach sinless perfection in this life. The Bible teaches that, while we are in the flesh, we will always struggle with a sin nature (see Romans 7:14-24). No one will be “perfect” (sinless) until we reach heaven.
The word translated “mature” in Ephesians 4:13 is the Greek word teleios. It is used throughout the New Testament to mean “perfect,” “complete,” “full-grown,” and “mature.” What Ephesians 4:13 teaches is that, the more we grow in Christ, the stronger and more unified we will be as a church. The verse does not teach that we will stop sinning.
Another passage that sometimes causes confusion is Colossians 1:28, which says, in some translations, that Paul wants to “present every man perfect in Christ Jesus.” Also, in Colossians 4:12 Paul prays that we would “stand perfect and complete in all the will of God.” In both verses, the word perfect should be translated as “mature” or “full-grown,” not “perfect,” in the sense of having no sin.
As human beings we are bound under the curse of Adam in this world. No matter how hard we try not to, we will still sin against God. The apostle Paul rebuked Peter for showing favoritism (Galatians 2:11-13). Late in his ministry, Paul calls himself the chief of sinners (1 Timothy 1:15). Peter, James, John, and Paul all admitted that they were imperfect. How could you or I claim anything different?
True perfection will not come until the Rapture of the church, when we rise to meet Jesus in the air (1 Thessalonians 4:17). At that time we will receive a new body (Philippians 3:20,21; 1 Corinthians 15:54). We will attend the Judgment Seat of Christ (2 Corinthians 5:10) where our works will be judged and rewards will be given (1 Corinthians 3:9-15). We will then live forever and reign with Christ in sinless perfection.