A Jehovah Witness and I spoke the other day and he explained to me that JWs believe that we'll live on earth after we die.
What scripture, if any, do they use to back this belief?
The idea comes from Revelations 21
The problem with interpreting Revelations is that there's a lot of debate on what it actually means.
Will we live on a new earth? Yes in the sense that God will give us a place to live.
Will it be identical to the old earth (with tornadoes, volcanoes, etc)? Who knows!
The New World Translation of this doesn't really vary. You can read that if you'd like.
Jehovah's Witnesses, as myself, believe in an earthly paradise. This paradise will be the restoration of what Adam and Eve lost when they sinned. We view Psalms 37:11, 29 as a prophecy of this restoration. Jesus will rule from heaven the humankind with 144000 corulers, including resurrected, for 1000 years. We believe that some prophecies for this time are the following:
Isaiah 45:18 (all quotations from the NIV)
Jehovah's witnesses will also use other bible texts to back up the idea of a 'paradise earth', although the exact combination of these two words do not appear in the bible and sometimes discussion can arise about the 'correct' interpretation of the word 'land/earth'.
The most important ones (or the first that come to my mind) are:
'Happy are the mildtempered ones since they will inherit the earth'
'Let your will take place as in heaven, also upon earth.'
'But there are new heavens and a new earth that we are awaiting according to his promise, and in these righteousness is to dwell.'
This idea of a new heaven and earth is also already known in the OT, e.g. Isaiah 66:22.
OT texts that stress a 'promised land' or the idea that the earth or righteous ones who inhabit it, will remain for ever, are also used to support the idea of a paradise earth: e.g. Deuteronomy 30:20; Psalm 37:29, Proverbs 2:21-22 (or a contrario Proverbs 10:30) and Ecclesiastes 1:4.
JW's further point to certain OT texts that heavily stress that humans have an earthly destination or that the earth is destined to be inhabited, e.g.:
Note: the difference in rewards for the faithful ones (eternal life in heaven or eternal life on a paradise earth) is based on a special interpretation of John 10:16 (the 'other sheep' are not interpreted as non-Jews, but as persons who look forward to live for ever on paradise earth and not in heaven).