What is the meaning of the saying: "The strength of the believer is in his heart and his weakness is in his body, and the hypocrite is the opposite"?

This saying attributed to some of the early Muslims (Salaf) means that a believer is concerned with purifying his heart and refining his soul, which makes him strong of heart, resolute in determination, and high-spirited. As for the hypocrite, he is concerned with the desires of his body and neglects his heart, so you find him always fearful and terrified, as Allah Almighty said: "They think every cry is against them." This does not mean that the believer neglects his body, for the Sharia (definition) commands seeking medical treatment, cleanliness, and maintaining good health.