It is narrated from Sa'd bin Ibrahim that he (peace and blessings be upon him) said: "Nor is it permissible for a strong and healthy person to ask for sadaqah." Ibrahim bin Sa'd narrated it from his father, and there is disagreement over him too about whether it is marfu' (attributed to the Prophet) and about its wording; and the narration of those who report it as marfu' is sufficient.
Al-mirrah means strength; its origin is the tight twisting of a rope.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الصدقات / 13158