A song written by Billy Edd Wheeler and popularized by The Kingston Trio, whose rendition peaked at number 33 on the Billboard chart in 1963. The song is told from the perspective of a thirsty cowboy crossing the desert. The cowboy comes across a well and a note from Desert Pete.
Desert Pete has left a jar full of water nearby, but cautions that there is only enough to prime the pump. The cowboy is admonished not to drink any water from the jar, but to have faith, prime the pump, and have all the water he wants, then leave the jar filled for others.
So, as Desert Pete says in the refrain,
You’ve got to prime the pump, you must have faith and believe
You’ve got to give of yourself 'fore you’re worthy to receive