The short answer: Because God is faithful. The long answer: Because God will do exactly what He promised in His Word. If we confess our sins, the blood of Jesus will cleanse it away. If we reckon our flesh to be dead and identify with Christ – that we are risen with Christ in the heavenly places – we will not reap the corruption of the flesh. If we study the Word as a workman who needs not to be ashamed, then we’ll be prepared for every good work. If we are doers of the Word and not hearers only, then the Lord will reward our works. If we exercise ourselves in obeying God, yet have patience because this journey will take a lifetime, then we’ll abide in Him. If we remember the Lord’s death for our sins, the giving of His body and blood, then we’ll have a right view of the horror of sin and steer clear of it more consistently.
In other words, if we meet the conditions of the promises, God will bless accordingly. God always keeps His promises toward those who are believing Him for them. So we can make confident choices now to prepare for the judgment because we know that God will do what He promised. The promises are conditional. Keep the conditions of the promises and God will do His part. For instance, 1 John 1:9 says, “If we confess our sins” (this is the condition), “He is faithful and just to forgive us” (this is the blessing). The blessing depends on the condition. If we refuse to acknowledge our wrong as sin, then we deprive ourselves of the blessing of sins forgiven.
Don’t simply believe in the promises. Pay attention to the conditions. Do you want God to show you mercy at the judgment? Then follow the promise carefully: “For if you forgive men their trespasses [the condition], your heavenly Father will also forgive you [the blessing]” (Matt. 6:14).
If I take the train that has a scheduled stop south in the next town, then I know I’ll reach the town south of me. I am on the right train. If I want to go south but get on a train going north, I will miss my appointment. Pay careful attention to the conditions that merit the blessings. To make your destination of being forgiven, get on the right train – do not hold grudges. Control your temper. Be gracious toward those who have done you wrong.
What if we don’t meet the conditions of the promise? What if we are taking the wrong train? “But if you do not forgive men their trespasses [the condition], neither will your Father forgive your trespasses [the consequence]” (Matt. 6:15). God will apply the blessing if the conditions are met. God will apply the warning if those conditions are met.
Because God is faithful with His promises and warnings, we can have complete assurance we will end our lives in blamelessness and holiness and love if we pursue the conditions for those promises.