1 Corinthians 3:16-17 says:
Do you not know that you are God’s temple and that God’s Spirit dwells in you? If anyone destroys God’s temple, God will destroy him. For God’s temple is holy, and you are that temple.
This text has been used, particularly by the Roman Catholic Church to say that if a person commits suicide, they go directly to Hell – no passing Go, no collecting $200.
“Mortal Sins” and “Venial Sins”
Using these verses as justification, the Roman Catholic Church labels suicide a “mortal sin,” for which no atonement can be made, as opposed to “venial sins” which a person may be cleansed of through paying for them via suffering in purgatory.
First of all, the entire idea of mortal and venial sins goes contrary to the clear teaching of Scripture, which states that there is only one unforgivable sin, which is the blasphemy of the Holy Spirit (click here for an explanation of the blasphemy of the Holy Spirit). Furthermore, it is only Jesus who atones for our sins, we cannot atone for any of our sins, and to claim that we can “pay” for our own sins through our sufferings is to negate and minimize the work of Jesus on the cross, and say that Jesus suffered and died in vain.
The key passage used by the Roman Catholic Church to justify this belief in mortal vs. venial sins is 1 John 5:16-17. I have written about those verses and what they mean here: What is the “Sin Unto Death,” and Why Should We Not Pray for It?
“You” and “Y’all”
In 1 Corinthians 3:16-17, Paul uses the plural form of “you” – in other words, he is saying: “All y’all (together) are the temple of God.”
What’s important to remember about this passage, is that Paul the Apostle is writing to the Corinthian church about their church. Some in the church were harming and tearing apart the church with their divisive attitudes and actions, and Paul is giving them a stern warning that if anyone destroys the temple of God (the Church which He loves), God will take that personally and not let is slide.
Later in 1 Corinthians, in chapter 6, Paul once again speaks of the Temple of God in relation to the indwelling of the Holy Spirit, but there he does so in regard to the individual believer. This passage in 1 Corinthians 3, however, is not written to or about the individual believer, but to the church about the church. So the point of the passage is not about suicide at all, but it is a warning to those who would harm and tear apart the church with their words and actions.
When Christians Were Killing Themselves
Until the Edict of Milan, AKA the Edict of Tolleration was issued in 313 AD, Christianity’s status in the Roman Empire was that of religio illicita, an “illicit” or illegal religion (as opposed to Judaism, which held the status of religio licita). During this time, Christians throughout the Roman Empire experienced waves of persecution, usually dependent on the attitudes of local authorities, although there were times when persecution was the official policy of the entire empire – such as during the reigns of Nero and Diocletian. Christians also faced persecution outside the Roman Empire.
During this period, many Christians were martyred, and martyrs were highly regarded and respected as those who had been willing to pay the ultimate price for their faith. In fact, martyrdom was so highly regarded, that people began to seek it out and desire it, as a way of expressing their devotion to Jesus. Ignatius of Antioch, for example, wrote about his desire to die as a martyr.
But some people took it even further. Jerome writes about a young woman named Belsilla who flagellated herself so much that she died from her self-imposed injuries. Another woman, Agathonike, upon witnessing the execution of a bishop by burning, also threw herself onto the fire, declaring “this is the meal that has been prepared for me.” She died in the flames, even though she had not been arrested nor charged. There are other accounts of Christians volunteering to be martyred even though they were not even being sought by the authorities. 
The Donatists, who considered themselves particularly hard core and dedicated (and looked down on those they considered less-committed, even to the point of questioning their salvation), greatly desired to show their devotion by being martyred. Some Donatists even went to the point of simply killing themselves to show how spiritual they were, i.e. how much they were not attached to this life and how much they desired to depart this world and be with Christ.
The Response of the Church
Seeking martyrdom and committing suicide became such a big issue with the Donatists in particular that it threatened the credibility, and even the existence of the church in their area of North Africa.
Judaism had always considered suicide to be sinful, whereas in pagan Roman culture it was considered an acceptable way to exit this life, and was practiced mostly by the wealthy, in part because slaves were not allowed to commit suicide since their lives did not belong to them, but rather to their masters.
It was Augustine of Hippo, a native of North Africa himself, who took up the challenge of addressing this issue and clarifying Christian thinking on this subject. In his book ‘The City of God’, Augustine considered what the Bible has to say about suicide and weighed various arguments for and against suicide. His conclusion was that suicide is always wrong as it is a violation of the sixth commandment (“Thou shall not murder”), and is never justified even in extreme circumstances. This became the official position of the church. 
Just because 1 Corinthians 3:16-17 isn’t talking about suicide, it must be noted that suicide is clearly a sin and is never the answer.