Obedience and sanctification are the true signs that a person has been spiritually saved by Jesus Christ. If salvation is the root, then obedience and sanctification can be called the fruit of a born-again believer. In the Bible, salvation isn't just a decision we make at one point in time, it is also a lifelong process of becoming more and more like Jesus Christ. This process involves the deep and intentional work of the Holy Spirit as He continually transforms our will, emotions, mind, heart and behaviour. It is during this time that we learn sinfulness of sin and seek to rid ourselves of it each and every day.
12 Therefore, my dear friends, as you have always obeyed—not only in my presence, but now much more in my absence—continue to work out your salvation with fear and trembling, 13 for it is God who works in you to will and to act in order to fulfill his good purpose. (Philippians 2:12-13)