The original is by Curtis Mayfield. On one of the later albums Bob and the Waliers recorded ("Exodus"?) it is listed as "One Love/People Get Ready." There are early Wailers versions of it from the 60's. They added the 'One Love' chorus.

PEOPLE GET READY
The Impressions
- words and music by Curtis Mayfield (1964)

People get ready, there's a train comin'
You don't need no baggage, you just get on board
All you need is faith to hear the diesels hummin'
You don't need no ticket you just thank the lord

People get ready, there's a train to Jordan
Picking up passengers coast to coast
Faith is the key, open the doors and board them
There's hope for all among those loved the most
There ain't no room for the hopeless sinner whom would hurt all mankind
Just to save his own
Have pity on those whose chances grow thinner
For there is no hiding place against the kingdoms throne

People get ready there's a train comin'
You don't need no baggage, just get on board
All you need is faith to hear the diesels hummin'
You don't need no ticket, just thank the lord.

Copyright 1964 Chi sounds (BMI)