"IF" also offers one the hope of having a wonderful life in this world, filled with the joy (Jn. 3:24; 15:11; etc.), the peace of Christ (Jn. 14:27; 16:33; etc.), and a glorious, eternal life spent with God forever (Jn. 3:15; 10:28; etc.)! God's Word, presented here in bold print, says, "That IF thou shalt confess with thy mouth the Lord Jesus, and (IF thou) shalt believe in thine heart that God hath raised Him from the dead, thou shalt be saved" (Rom. 10:9). The following verse explains the importance of those two factors in our salvation: "For with the heart man believeth (in the resurrected Lord) unto righteousness; and with the mouth confession (of Jesus as one's Lord) is made unto salvation" (Rom. 10:10). These two factors were revealed earlier in the Book of Romans:
"Being justified freely by His grace through the redemption that is in Christ Jesus: whom God hath set forth to be a propitiation through faith in His blood, to declare His righteousness for the remission of sins that are past, through the forbearance of God; to declare, I say, at this time His righteousness: that He might be just, and the justifier of him which believeth in Jesus" (Rom. 3:24-26).
And, just as there are two factors involved in one being born again, there are two factors which reveal our status as being children of God: born again believers cannot help but warn others of the danger they are in if they do not trust in Jesus, and believers and unbelievers alike, will be able to see that our words match our lives. That is how the Church grew so rapidly at the beginning: they were "Praising God, and having favour with all the people. And the Lord added to the church daily such as should be saved" (Acts 2:47). James wrote of the need for one's life to match his testimony (Jam. 1:21-27).
"IF" you are born again, you, and others, will have no problem knowing it!