Every Christian has a phase in their walk with Christ where they suffer doubt as to whether they are saved or not. This usually occurs during the Spiritual Infancy stage through the Childhood stage. Some Christians remain in these stages of immaturity their whole lives and fail to move into Spiritual Adulthood. Because of this, they don't move on to Spiritual Parenthood either. However, just like in the physical world infancy and childhood are healthy phases to be in and it seems at the time to take quite a while. And so it is healthy during these phases to have doubts regarding assurance of salvation but as it is not good for a person to remain in the infant stage in their physical development so too it is not good for a person to remain so in their spiritual development.
Some may wonder "Is knowing that I am saved even possible?" I John 5:13 suggests that it is indeed possible "I write these things to you who believe in the name of the Son of God, that you may know that you have eternal life." Notice here the words "that you may KNOW that you have eternal life." Many of the things written in I John are there to give people assurance of whether they have eternal life or not. Notice that John is clearly stating that a person can indeed know with certainty of their standing with God.
Another point in seeking assurance is from Romans 8:16. "The Spirit Himself bears witness with our spirit that we are the children of God." A person can know that they are saved as the Holy Spirit who lives inside them speaks to their heart that they are saved. God through the Spirit speaks with our Spirit that we are His children. Let me stress to you that this is absolutely essential to assurance!
So, how does Spirit speak to our spirits? What does He use? What types of things do we need to do in order to hear His voice? The Holy Spirit speaks with our spirits using the scripture. Notice what Peter wrote in 2 Peter 1:21 "No prophecy (prophecy of scripture) was ever produced by the will of man, but men spoke from God as they were carried away by the holy Spirit." The is the product of the Holy Spirit, and the Spirit uses the Bible to speak to our spirits.
