The Prophet ﷺ said, "Many a person with disheveled hair, covered in dust, and dressed in two worn-out garments, if he were to swear an oath by Allah, Allah would fulfill it for him."
أن النبي ﷺ قال: رب أشعث أغبر ذي طمرين لو أقسم على الله لأبره.
Narrated by Abd bin Humayd (1236, Muntakhab), Bazzar (6459), and Tabarani in Awsat (5054, Majma Bahrayn), all of them through the route of Usama bin Zayd, from Hafs bin Ubaydullah bin Anas, from his grandfather Anas, who mentioned it. Its isnad is hasan because of Usama bin Zayd, for he is hasan al-hadith.Tirmidhi (3854) narrated it through another route from Anas with the same wording, adding at the end, "and among them is Bara bin Malik," and said, "This is a hasan hadith."On this subject there is also a report from Thawban, who said, the Messenger of Allah ﷺ said, "Among my nation are those who, if one of you came to him and asked him for a dinar, he would not give it to him, and if he asked him for a dirham, he would not give it to him, and if he asked him for a fils, he would not give it to him, yet if he asked Allah for Paradise, Allah would grant it to him. A man of two worn garments, given no regard, if he swore an oath by Allah, Allah would fulfill it for him."Tabarani narrated it in Awsat (5048) from Muhammad bin Ibrahim Assal, who said, Sahl bin Uthman told us, Abu Muawiya told us, from Amash, from Salim bin Abu Jaad, from Thawban, who mentioned it.Haythami said in Majma (10/264), "Tabarani narrated it in Awsat and its men are the men of sahih." I say, it is as he said, except that its isnad is disconnected, for Salim bin Abu Jaad did not meet Thawban and did not hear from him. This was stated by Ahmad, Abu Hatim, and Bukhari. See Tuhfat Tahsil (p. 120).Nevertheless, Munziri graded it sahih in Targhib (4817), and Iraqi followed him in that.