if you scratch my back, then I will scratch yours
Definition:  if somebody helps you, you will in return help them back (by so doing you are returning the favour they once gave)
Usage:  a month ago, Thabo found me stuck as I was out of petrol; he towed my car to the nearest petrol station, I guess he remembered that I once did the same; talk about if you scratch my back, then I will scratch yours

SEPEDI
Translation:  ge o ngwaya mokokotlo wa ka, le nna ke tla ngwaya wa gago
Proverb: go fa ke go fega, wa kwa tlala wa fegolla

XITSONGA
Translation:  loko u ni n’waya nhlana, na mina ndzi ta n’waya wa wena
Proverb: xandla famba, xandla vuya

TSHIVENḒA
Translation:  arali wa kweta muṱana wanga, na nṋe ndi ḓo kweta wau
Proverb: tshanḓa i ya, tshanḓa vhuya