Will sin be possible in heaven?

To answer the question will sin be possible in heaven, there are a number of passages we should look at. 

“…the assembly of the firstborn who are enrolled in heaven, and to God, the judge of all, and to the spirits of the righteous made perfect“ (Hebrews 12:23). 

“…those whom He foreknew He also predestined to be conformed to the image of His Son…” (Romans 8:29).

“No longer will there be anything accursed, but the throne of God and of the Lamb will be in it, and his servants will worship Him” (Revelation 22:3).

“…nothing unclean will ever enter it, nor anyone who does what is detestable or false, but only those who are written in the Lamb’s book of life” (Revelation 21:27).

“The one who conquers, I will make him a pillar in the temple of my God. Never shall he go out of it, and I will write on him the name of my God…” (Revelation 3:12).

“I will plant them on their land, and they shall never again be uprooted out of the land that I have given them…” (Amos 9:15).

Christians will be made “made perfect” (Heb. 12:23). They will be “conformed into the image” of Jesus (Rom. 8:29). It may be that Christians can sin, but won’t sin because they will not want to sin. 

When Christians see Jesus, they shall be like Him (1 John 3:2). That is the sense in which Christians will be unable to sin (non posse peccare, as Augustine said). Christians will be like Christ!

So, no. Ultimately, Christians will not be able to sin in heaven. But it won’t be from an external constraint but from internal renewal. 

Christians will finally completely have their affections rightly aligned with reality. Christians will love the LORD their God with all their heart, soul, mind, and strength.