To what extent is the hadith sound in which Jabir ibn Abdullah (may Allah be pleased with him) narrated that the Prophet (peace and blessings be upon him) supplicated in Masjid al-Fath for three days, and his supplication was answered on Wednesday between the two prayers, and that Jabir used to seek out that hour for supplication?

The hadith (definition) that narrates the answering of the Prophet's (peace be upon him) supplication on Wednesday at Masjid al-Fath is weak, due to two defects in its chain of transmission (isnad (definition)): The first is Kathir bin Zayd al-Aslami, who is considered weak. The second is Abdullah bin Abd al-Rahman bin Ka'b bin Malik, whose status is unknown (majhul al-hal). Furthermore, Kathir was inconsistent in narrating this hadith. Even if the hadith were authentic, its intent would be to seek out the time for supplication, not its specific place, as Jabir (may Allah be pleased with him) did.