This is a discussion thread for the Daily Spanish Word (http://daily.tomisimo.org/) for September 15, 2008

rascar - verb - to scratch. Look up rascar in the dictionary (http://www.tomisimo.org/dictionary/spanish_english/rascar)

Si rascas mi espalda te rascaré la tuya.
If you scratch my back I'll scratch yours.

Rasgar means to tear or to rip.
Rasgarse las vestiduras = To rend/tear/rip one's clothes

Rascar means to scratch.
Rascar la espalda = To scratch one's back.
Scratch my back and I'll scratch yours = Hoy por mí, mañana por ti

Fixed the typo. And good point with the idiom. :)