Matt. 5:26,18:34; Luke 12:58-59 – Jesus teaches us, “Come to terms with your opponent or you will be handed over to the judge and thrown into prison. You will not get out until you have paid the last penny.” The word “opponent” (antidiko) is likely a reference to the devil (see the same word for devil in 1 Pet. 5:8) who is an accuser against man (c.f. Job 1.6-12; Zech. 3.1; Rev. 12.10), and God is the judge. If we have not adequately dealt with satan and sin in this life, we will be held in a temporary state called a prison, and we won’t get out until we have satisfied our entire debt to God. This “prison” is purgatory where we will not get out until the last penny is paid.
Matt. 5:48 - Jesus says, "be perfect, even as your heavenly Father is perfect." We are only made perfect through purification, and in Catholic teaching, this purification, if not completed on earth, is continued in a transitional state we call purgatory.
Matt. 12:32 – Jesus says, “And anyone who says a word against the Son of man will be forgiven; but no one who speaks against the Holy Spirit will be forgiven either in this world or in the next.” Jesus thus clearly provides that there is forgiveness after death. The phrase “in the next” (from the Greek “en to mellonti”) generally refers to the afterlife (see, for example, Mark 10.30; Luke 18.30; 20.34-35; Eph. 1.21 for similar language). Forgiveness is not necessary in heaven, and there is no forgiveness in hell. This proves that there is another state after death, and the Church for 2,000 years has called this state purgatory.
Luke 12:47-48 - when the Master comes (at the end of time), some will receive light or heavy beatings but will live. This state is not heaven or hell, because in heaven there are no beatings, and in hell we will no longer live with the Master.
Luke 16:19-31 - in this story, we see that the dead rich man is suffering but still feels compassion for his brothers and wants to warn them of his place of suffering. But there is no suffering in heaven or compassion in hell because compassion is a grace from God and those in hell are deprived from God's graces for all eternity. So where is the rich man? He is in purgatory.
1 Cor. 15:29-30 - Paul mentions people being baptized on behalf of the dead, in the context of atoning for their sins (people are baptized on the dead’s behalf so the dead can be raised). These people cannot be in heaven because they are still with sin, but they also cannot be in hell because their sins can no longer be atoned for. They are in purgatory. These verses directly correspond to 2 Macc. 12:44-45 which also shows specific prayers for the dead, so that they may be forgiven of their sin.
Phil. 2:10 - every knee bends to Jesus, in heaven, on earth, and "under the earth" which is the realm of the righteous dead, or purgatory.
2 Tim. 1:16-18 - Onesiphorus is dead but Paul asks for mercy on him “on that day.” Paul’s use of “that day” demonstrates its eschatological usage (see, for example, Rom. 2.5,16; 1 Cor. 1.8; 3.13; 5.5; 2 Cor. 1.14; Phil. 1.6,10; 2.16; 1 Thess. 5.2,4,5,8; 2 Thess. 2.2,3; 2 Tim. 4.8). Of course, there is no need for mercy in heaven, and there is no mercy given in hell. Where is Onesiphorus? He is in purgatory.
Heb. 12:14 - without holiness no one will see the Lord. We need final sanctification to attain true holiness before God, and this process occurs during our lives and, if not completed during our lives, in the transitional state of purgatory.
Heb. 12:29 - God is a consuming fire (of love in heaven, of purgation in purgatory, or of suffering and damnation in hell).
1 Cor. 3:10-15 - works are judged after death and tested by fire. Some works are lost, but the person is still saved. Paul is referring to the state of purgation called purgatory. The venial sins (bad works) that were committed are burned up after death, but the person is still brought to salvation. This state after death cannot be heaven (no one with venial sins is present) or hell (there is no forgiveness and salvation).
1 Cor. 3:15 – “if any man’s work is burned up, he will suffer loss, though he himself will be saved, but only as through fire.” The phrase for "suffer loss" in the Greek is "zemiothesetai." The root word is "zemioo" which also refers to punishment. The construction “zemiothesetai” is used in Ex. 21:22 and Prov. 19:19 which refers to punishment (from the Hebrew “anash” meaning “punish” or “penalty”). Hence, this verse proves that there is an expiation of temporal punishment after our death, but the person is still saved. This cannot mean heaven (there is no punishment in heaven) and this cannot mean hell (the possibility of expiation no longer exists and the person is not saved).
1 Cor. 3:15 – further, Paul writes “he himself will be saved, "but only" (or “yet so”) as through fire.” “He will be saved” in the Greek is “sothesetai” (which means eternal salvation). The phrase "but only" (or “yet so”) in the Greek is "houtos" which means "in the same manner." This means that man is both eternally rewarded and eternally saved in the same manner by fire.
1 Cor. 3:13 - when Paul writes about God revealing the quality of each man's work by fire and purifying him, this purification relates to his sins (not just his good works). Protestants, in attempting to disprove the reality of purgatory, argue that Paul was only writing about rewarding good works, and not punishing sins (because punishing and purifying a man from sins would be admitting that there is a purgatory).
1 Cor. 3:17 - but this verse proves that the purgation after death deals with punishing sin. That is, destroying God's temple is a bad work, which is a mortal sin, which leads to death. 1 Cor. 3:14,15,17 - purgatory thus reveals the state of righteousness (v.14), state of venial sin (v.15) and the state of mortal sin (v.17), all of which are judged after death.
1 Peter 1:6-7 - Peter refers to this purgatorial fire to test the fruits of our faith.