How do you know for sure that you are saved?
How do you know for sure if you are saved? How do you know that you are not deceiving yourself? How can you be absolutely sure?
Important question. Assurance of salvation isn't not something to take lightly especially when we know we can deceive ourselves in this aspect. In Matt. 7 the Lord warns about those who come to heaven's gate without the spiritual relationship with God through Christ.
To answer your question I will make use of a portion of the rich heritage of our Reformed writings. This time let me use the Canons of Dordt. These articles deal with many different subjects of doctrine but one of them is also about the assurance of faith. I assume you have access to the Canons of Dordt so I don't have to write out the entire article. If not, I am sure you will let us know. You can find the Psalter on-line on our website and in the back part, pages 96 and onward, you will find the Canons.
Let's first go to Art 12 of chapter 1 (page 99). There is stated that God's elect shall find out in different ways and different strength the assurance of their salvation. Not everyone will be equally assured of their salvation. The reason one will be saved is because of God's election, a deed of God's will from all eternity in which He has determined who will be His people. This is completely hidden from our sight. Yet one will know his/her election by the fruits of this election. In other words, by God's work within the heart will you know whether He has chosen you. One way of assurance is therefore by "observing in yourself the unmistakable fruits of election." What are those fruits? Notice that they list a few of the saying of the Lord in Matt. 5. In that chapter the Lord Jesus gave us 7 personal-descriptive characteristics of someone who is born again. Now meditate or study these seven characteristics of God's heart-renewing grace. Compare yourself with those seven marks. You can never go wrong with these marks. No matter what kind of conversion experience you have had, these seven statements are to be reflected in your life. Paul and Samuel would recognize each other in these sayings though both of them had such a different conversion story to tell. I always say that your "conversion story isn't the proof of being saved." It is the marks of the Lord Jesus which you are to find in your heart. If you have access to books, pick up Thomas Watson's book on the Beatitudes. Otherwise, I did preach a series on these verses and so you can check the archives of our website on that. If they aren't there, let me know and I see if they can still be added on there.
The next article that deals with assurance is in Head 5, art, 10 (page 113). Notice that in this article we are taught that assurance doesn't come through some spectacular revelation of God. Some people may speak about visions and voices or other unique events in their life by which they are assured of their salvation. The authors of this article didn't go that way. They again lead us back to the Scripture. God uses always His Word through His Spirit to assure His children of their salvation. He kindles faith in the promises of the Gospel. There are plenty of them in the Bible given for our comfort. However, so often we don't dare to believe those promises. But the Spirit will kindle at His time and His measure a faith in those promises. The more faith in those promise, the stronger our assurance will be. Especially when the Spirit joins His testimony to our spirit. In the first point we notice that 'our spirit' can observe the very marks or characteristics that I am alive. At this moment, my own spirit testifies that I am alive: I am breathing, typing, thinking, talking! So also spiritually our own spirit or soul can testify, "One think I know, once I was blind but now I see." Yet when the Spirit bears witness through the Word, under the preaching or your personal reading or even meditating on His Word, then our assurance of salvation will be the stronger.
That article then also point out that the desire and effort to be holy is an indication that there is spiritual life in you. Man hungers for happiness; renewed man hungers for holiness and will never feel happy except they are holy. So if you find in yourself the inner desire to be holy and strive for that day after day, looking to Christ and using His means of grace, you have a spiritual mark of being born again. See also question 86 of the Heidelberg Catechism (page 66).
Lastly, in the Canons after Head 5, you find a section of 'rejections.' Let's go to rejection nr 5 (page 115). In this rejection the Synod men torpedo a sentiment that you can only be assured of your salvation if you have indeed some great and wonderful special revelation. They mean with that a 'revelation' that is without the Word of God and consist of some mystical experiential event. Their answer is so Scriptural. Notice how they again point to the marks of grace. They use the word "deduce." That is conclude. If I can find in myself those marks of God's Spirit's gracious renewal, I may draw the joyful conclusion that His work is in me.
Hopefully this will give you some direction in searching for this answer. The work of the Holy Spirit within us is the 'spiritual forensic evidence' that He is working and living there. People are put into prison because their 'fingerprints were found at the crime scene.' Likewise, when I can find or trace the fingerprint of the work of the Holy Spirit within me, I am to thank the "Father that He has made me meet to be a partaker of the inheritance of the saints in light."