«فَالْبَيْتُ مِثْلُ الشَّمْسِ»
The ancestral house is like the sun.
Bayt can refer to a dwelling, but also to one's house or family line. Associated words about radiance and great standing signal fame and rank rather than the literal brightness of a building.
Mithl marks an explicit simile: the family house is the thing compared, and the sun is the point of comparison. This elevated self-description prepares a poignant contrast with the speaker's later account of hardship.