Dictionary.com defines assurance (as·sur·ance) as:
1. a positive declaration intended to give confidence: He received assurances of support for the project.
2. promise or pledge; guaranty; surety: He gave his assurance that the job would be done.
3. full confidence; freedom from doubt; certainty: to act in the assurance of success.
Wikipedia states that assurance is a Protestant Christian doctrine that states that the inner witness of the Holy Spirit allows the justified disciple to know they are saved.
's compact bible dictionary defines it as the following. The state of beings assured; freedom from doubt and uncertainty. As a theological concept refers to the believers' full confidence and conviction that the penalty of their sins have been paid and that heaven has been secured as their eternal destiny as by Christ's death and resurrection.
Those true Christians who have repented (to change one's mind about Christ) from their ways, believed on Jesus' death as atonement for their sins (He died for them all once and for ever), and been baptized in His name (as it alone has been commanded; containing all saving power) are experiencing the blessed assurance of God.
Those today are looking for direct results. The shortest route or distance between two objects is a straight line. In other words results. Now from personal first hand experience, I can tell you that anyone that prays a non biblical prayer of salvation will not find it. Nor will those baptized into a triune god system (either as an adult or baby). The fact is if a church's salvation is not based on the bible (the scriptures or word of God) then they have nothing to offer you except a form of religion. There are many theological terms I could employ to make this sound more effective or technical but those concepts might not be really understood even by some real Christians. So that would be totally useless.
The fact is that I am not here to waste your time or mine. Therefore consider these facts. After repenting of your ways and confession of your belief in Jesus Christ as the only means of salvation, and baptism (full immersion as defined historically and biblically) in His name alone you, will feel, see and know the following things. A new regeneration or infilling of the Holy Spirit. This will place or plant thoughts from above in your mind. Giving you greater perceptions about the singularity of God, life, and scriptural wisdom. It's kind of like when you read the red letter edition or underlined words of Christ. You simply know and feel the difference. God will begin to talk to you on a personal level. His spirit will stir you up to do good works in His name. Also when He moves you will feel it in a tangible form. Sometimes God will tell or show of things to come or perhaps reveal a demonic inspired spirit in some one's deeds or actions.
Now I am not saying nor implying that non Christians do not feel the move of God upon them. As God uses His spirit to draw or bring them into further truth. Obviously the grace of God has appeared to all men, but we must continually seek the Lord and His strength for a greater revelation or walk with him. As it is a marriage and not simply a one time union. The same would also apply to those who already received a smaller portion of His spirit with speaking in tongues. Though they would have a greater witness within them than others. Yet they still are short of the true fullness of the godhead revelation and salvation. As Cornelius had to be baptized in the name of the Lord Jesus for salvation. Peter himself, who previously commanded this for all the Jews, did said so for every gentile believer regardless of any gifts that God had already imparted upon them. Acts chapters 2, 8, and 10 relax that same message.
So what are you waiting for? Do you want to please someone instead of the creator of the whole earth? Are you asking for the failed wisdom of men instead of the Divinely inspired and never failing one of God? Who can save you from divorce, bankruptcy, hatred, strife or even your self? The answer is nobody! Jesus is the answer for the world today. There is not a problem that He has not already solved nor a solution which He has not already come up with. There are literally hundreds of men and women who have been inspired whether in a dream, vision, or in word to do a great thing for humanity. This all comes from the hand or if you wish, the power of God's spirit. And this was directed to give Him praise and glory all the while fulfilling the needs of mankind in the process.
Lastly I know that this message is not for everyone. Some will hear and not receive it. Others will simply mock it. While others may hear and receive the Gospel for a time but other things will crowd it out. Still there will always be a few faithful believers in God's word. I did not say in a church or religion. The word of God alone must be used to find the truth. Therein you will find that the name of the father is Jesus. That the son was called Jesus. And that the Holy Spirit was sent in the name of Jesus ( :43, 14:26; Matthew 1:21; Ephesians 3:14-15). Nobody was baptized into a trinity within the scriptures. That word or concept came much later and was formally adopted in the year of 325 A.D. by the Catholic dominated council of Nicaea. Check the church records of Acts 2:38-22:16 or all of Paul's letters; it was done in the name of Jesus, Jesus Christ or the Lord Jesus Christ. And one does not mean the same as the other (Ephesians 4:5; Colossians 3:17 and Acts 4:10-12). If any man or woman lack wisdom let him/her ask of God by faith, and it will given them in this matter or others. Don't go asking some Pharisee who is deceived himself and merchandising you. Instead go the source of all life - God Himself. If you had a serious medical problem would you go to see a veterinarian? If your house had insect infestation or termites would you go to a dentist to solve your problem? If your sink was overflowing with water everywhere would you call a lawyer? No. Why go to the rest when God already gave you the best solution, His word. If you still doubt then ask Him in prayer to show you the truth. He will never lead or guide you in a wrong or unjust path. His way is one of assurance and truth. Trust in Him. He will never leave nor forsake His people but instead save them from their sins. To be His you must have His family name of Jesus. May God be with you always!