Sayyiduna Qabisah bin Mukhariq (may Allah be pleased with him) says: I came to the Prophet (peace and blessings be upon him) to ask him about my debt. He (peace and blessings be upon him) said: "Asking is unlawful except for three people: one is the person on whom there is the burden of a debt; it is lawful for him to ask until he pays off his debt, then he should refrain from asking. The second is the man struck by some calamity that destroys all his wealth; it is also lawful for him to ask until he reaches a comfortable state, then he should refrain from asking. The third is the man who is afflicted by some need or struck by poverty, and three reliable men of his people testify (to it); then it is also permissible for him to ask. Asking apart from this is unlawful."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الصدقات / 13193