Plegaria a un labrador (Víctor Jara)

Plegaria a un labrador is literally prayer to a worker, but when Victor Jara first performed this song in the late 1960s he said it was was specifically a call to the peasants who cultivated the land with their hands, to join with their brothers in the struggle for a fairer society. Check Wikipedia for the tragic and inspirational story of Victor Jara.

Levántate y mira la montaña	Arise and behold the mountain
de donde viene el viento, el sol y el agua.	from whence come (the) wind, (the) sun and (the) water.
Tú que manejas el curso de los ríos,	You who drive the course of (the) rivers,
tú que sembraste el vuelo de tu alma.	You who beget the flight of your soul.
Levántate y mírate las manos	Arise and behold (the=)your hands
para crecer estréchala a tu hermano.	to grow embrace your brother.
Juntos iremos unidos en la sangre	Together we will go, united in (the) blood
hoy es el tiempo que puede ser mañana.	now is the time that can be tomorrow.
Líbranos de aquel que nos domina	Deliver us from that which us dominates
en la miseria.	in (the) misery.
Tráenos tu reino de justicia	Bring your kingdom of justice
e igualdad.	and equality.
Sopla como el viento la flor	Blow like the wind the flower
de la quebrada.	of the ravine.
Limpia como el fuego	Clean like (the) fire
el cañón de mi fusil.	the barrel of my gun.
Hágase por fin tu voluntad	Have at last thy will
aquí en la tierra.	here on (the) earth.
Danos tu fuerza y tu valor	Give your strength and your courage
al combatir.	to fight.
Levántate y mírate las manos	Arise and behold (the=)your hands
para crecer estréchala a tu hermano.	to grow embrace your brother.
Juntos iremos unidos en la sangre	Together we will go, united in (the) blood
ahora y en la hora de nuestra muerte.	now and in the hour of our death.
Amén.	Amen.

Levántate y mira. I usually avoid self-consciously poetic translations like arise and behold, but in this case echoes of the biblical language of the Lord's Prayer are important. Though because tu isn't archaic in Spanish I've mostly avoided thou and thy.
El viento, el sol y el agua. I've put the in brackets if we'd drop it in English.
Estréchala has many other meanings, including accept and honour.
Sopla como el viento la flor de la quebrada. Second edit: I wasn't happy with my translation, so I referred it to a WordReference forum. Bandama suggests Blow on the valley flower, as the wind does, which makes a lot more sense than what I'd originally come up with. (For the purpose of the song, let's not get too hung up on the difference between a mountain valley and a ravine.) And Adolfo Afogutu points out a secondary meaning of flor: cream, or best of; just as several english knights were described as being the “flower of chivalry”, perhaps the flowers of the valley/ravine are the guerillas from that area. This could be Jara's poetic way of telling the guerillas to blow like the wind.

I found what I think may be the original lyrics on the official website maintained by Joan Turner Jara, Victor's wife; the image just appears with no explanation. Click it to see it slightly larger.

I'm not aware of any recordings of the choral version, but you can hear Victor himself sing the song with his group Quilapayún on YouTube.