1 Then he showed me the river of the water of life, clear as crystal, flowing from the throne of God and of the Lamb
The water of life flowing from the throne of God and the Lamb is in reference to those who will inherit the kingdom of heaven, that eternal life has been given to them.
2 down the middle of the city’s main street. The tree of life was on each side of the river, bearing twelve kinds of fruit, producing its fruit every month. The leaves of the tree are for healing the nations
The tree of life represents eternal healing with no more death, sickness, and any other illnesses.
3 and there will no longer be any curse. The throne of God and of the Lamb will be in the city, and his servants will worship him.
“and there will no longer be any curse.” Brings back to mind, Genesis 3:16-19 which makes a woman’s labor painful, hard work for men, spiritual [separation from God because of sin] and physical death for all humanity.
In the new heaven and the new earth, there will be no more curses as seen in Genesis 3, for sin will never again take root. The Lamb and the Lord God will be worshiped in pureness from His saints.
4 They will see his face, and his name will be on their foreheads.
We will see Jesus in His full glory. His name being on our foreheads signifies that we belong to Him forever.
5 Night will be no more; people will not need the light of a lamp or the light of the sun, because the Lord God will give them light, and they will reign forever and ever.
The Lord God Almighty who is pure light will be our sun. The night will not be necessary because as eternal beings, we will need no rest. Also, see notes in Revelation 21:25