In His Sermon on the Mount, Jesus stated: "In a word, you must be made perfect as your heavenly Father is perfect" (Mt 5:48). We must be "perfect in holiness...irreproachable at the coming of our Lord Jesus Christ" (1 Thes 5:23). The Lord commands us: "Become holy yourselves in every aspect of your conduct, after the likeness of the Holy One Who called you" (1 Pt 1:15). Without perfect holiness, we cannot "see the Lord" and be with Him forever in heaven (Heb 12:14).
After we have been baptized and have given our lives to Jesus as our Lord, Savior, and God, we begin walking "the road to holiness" (2 Pt 2:21). This is a long road, and sometimes we do not fully accept God's grace to become perfectly holy. If we die without complete holiness, the Lord will have mercy on us whom He has saved. He will give us time after death to complete our purification and growth in holiness. Although it is much better to do our purgatory of reparation, purification, and transformation before our deaths, the Lord gives hope and mercy to those not completely sanctified before death.
Purgatory shows that the Lord insists on our holiness, graces us to become holy, has mercy on us, and gives us hope. Thank God for grace, salvation, sanctification, and purgatory.