Question: "How can I have assurance of my salvation?"
Answer: How can you know for sure if you are saved? Consider 1 John 5:11-13 (NLT): "And this is what God has testified: He has given us eternal life, and this life is in his Son. So whoever has God's Son has life; whoever does not have his Son does not have life. I write this to you who believe in the Son of God, so that you may know you have eternal life." Who is it that has the Son? Those who have believed in Him and accepted Him (John 1:12). If you have Jesus, you have life. Eternal life. Not temporary, but eternal.
God wants us to have assurance of our salvation. We cannot live our Christian lives wondering and worrying each day whether we are truly saved or not. That is why the Bible makes the plan of salvation so clear. Believe in Jesus Christ and you will be saved (John 3:16; Acts 16:31). Do you believe that Jesus is the Savior, that He died to pay the penalty for your sins (Romans 5:8; 2 Corinthians 5:21)? Are you trusting Him alone for salvation? If your answer is yes, you are saved! Assurance means to "put beyond all doubt." By taking God's Word to heart, you can "put beyond all doubt" the fact and reality of your eternal salvation.
Jesus Himself states this regarding those who have believed in Him: "I give them eternal life, and they will never perish. No one will snatch them away from me, for my Father has given them to me, and he is more powerful than anyone else. So no one can take them from me" (John 10:28-29 NLT). Again, this gives more emphasis to "eternal." Eternal life is just that--eternal. There is nobody, not even yourself, who can take Christ's God-given gift of salvation away from you.
Memorize these passages. We hide God's Word in our hearts so that we do not sin against Him (Psalm 119:11), and this includes doubt. Take joy in what God's Word is saying to you: That instead of doubt we can live with confidence! We can have the assurance from Christ's own Word that the state of our salvation will never be in question. Our assurance is based on God's love for us through Jesus Christ. Jude 24-25, "To Him who is able to keep you from falling and to present you before his glorious presence without fault and with great joy - to the only God our Savior be glory, majesty, power and authority, through Jesus Christ our Lord, before all ages, now and forevermore! Amen."