The Greek terms that are translated “spirit” and “flesh” are a fundamental contrast, but one which is variously expressed in different languages. Often, however, “spirit” is equivalent to “heart” (Eastern Highland Otomi, Loma, Guerrero Amuzgo, Highland Puebla Nahuatl), and “flesh” may be rendered as “body” (Guerrero Amuzgo, Highland Puebla Nahuatl, Tzeltal) or “you yourself” (Central Tarahumara).
The following translations are illustrative of the contrastive expressions: “your hearts are ready but your bodies are weak” (Highland Puebla Nahuatl), “your heart is strong but you yourselves are not strong” (Central Tarahumara), “your heart has strength, but your body does not have strength” (Tzeltal), “your heart desires to do good, but your heart is weak,” in which “heart” must be used in both clauses since it not only stands for the center of the personality, but is also the symbol of typical human nature (Loma). (Source for this and all above Bratcher / Nida)
In Guhu-Samane an idiomatic expression with “your desire is there, but sleep has slain your body” is used. (Source: Ernest Richert in Notes on Translation December 1963: p. 4-7; reprinted in The Bible Translator 1965, p. 198ff.)