It depends on your flavor of Christianity.
Wars have been fought over this question for centuries.
- Simple answer: either you behave or you believe.
- Long answer:
The question is usually phrased like this: “What makes you a just person?”
There is a difference between Catholicism, Orthodoxy, Anglicanism and Methodism on one side and Luteranism-Calvinism on the other.
The majority of Christians, that is Catholics (1.200 million), Orthodox (300 million), Anglicans (85 million) and Methodists (75 million) think that you are just by your deeds.
You can be an atheist or a Muslim but if you strive all your life to do God’s will you are sanctified and you go to Heaven.
They argue, Bible in hand, using James 2:14-26, Galatians 5:19-21 and Matthew 19:17, that you have to avoid sin.
So, if you do not worship Jesus Christ but you behave, all is kosher (pun intended).
Lutherans and Calvinists (around 400 million) believe that you have to worship J.C. because you are just if you have faith and that does not depend on your merits or actions, as it is a gift from God.
So, if you are a Muslim or an atheist or, worse, a Catholic, Orthodox, Anglican or Methodist, then you go to Hell.
They pick from the Bible Eph 2:8, as well as Acts 16:14 and Phil 1:2 to prove they are right.
Justification (theology) – Wikipedia
So, pick carefully. Wings and halo are not going to descend by themselves on you.
I have a friend that insist on doing good deeds, have faith, circumcise, pray towards Mecca, understand that the world is an illusion, pray to Wiccan gods, etcetera, etcetera, all at the same time.
He says he doesn't want to go to Hell based on a technicality.
I have wise friends, let me tell you.