End of suffering (Isaiah 25-35, Rev 21:4)

 Reading the Basic Doctrines provided by BSF, preparing for OT role and training this weekend. I have a close friend who is Buddhist. A foundation of Buda is suffering caused by the ego interpreting nature as good or bad with the ultimate resolution of indifference leading to non-existence (Nirvana). This is counter the Christian understanding of the cause and destiny of suffering.  Here's an excerpt of the Christian doctrine of suffering:

Suffering is the experience of physical, mental, emotional or spiritual pain and/or distress. Suffering entered the world as a consequence of the fall of Adam and Eve and will be eternally abolished in the new heaven and new earth (Genesis 3; Revelation 21)....Some possible reasons for suffering include loving discipline, purification and/or an increased intimacy with Jesus Christ while other reasons for suffering remain mysteriously hidden (Proverbs 3:12; Romans 5:1-5; Philippians 3:7-10). Regardless of the type, purpose or reason of the suffering, no suffering is outside of God’s sovereign rule (Isaiah 45:7). Rather, God is able to use it for good (Genesis 50:15-21; Romans 8:28)...God has promised the suffering of His people will eventually end (Revelation 21:4). Until then, believers should expect to share in the suffering of Jesus Christ as a result of taking up their cross and following Him in a hostile world (Mark 8:34-35; Romans 8:17-18; Colossians 1:24).

I looked up Rev 21:4 and found references to Isaiah that made me want to understand the broader context between Isaiah 25 and 35.

He will wipe every tear from their eyes, and there will be no more death or sorrow or crying or pain. All these things are gone forever.” Rev 21:4

He will swallow up death forever. The Lord GOD will wipe away the tears from every face and remove the disgrace of His people from the whole earth. For the LORD has spoken. - Isaiah 25:8

So the redeemed of the LORD will return and enter Zion with singing, crowned with everlasting joy. Gladness and joy will overtake them, and sorrow and sighing will flee. - Isaiah 35:10

So the redeemed of the LORD will return and enter Zion with singing, crowned with everlasting joy. Gladness and joy will overtake them, and sorrow and sighing will flee. - Isaiah 51:11

Your sun will no longer set, and your moon will not wane; for the LORD will be your everlasting light, and the days of your sorrow will cease. - Isaiah 60:20

I will rejoice in Jerusalem and take delight in My people. The sounds of weeping and crying will no longer be heard in her. - Isaiah 65:19