To what extent is the statement true regarding the light emanating from homes where people perform الليل (night prayers), and angels seeing that light, and their inquiring about the worshipper if they do not see the light, and their supplication for him? And to what extent is the story true regarding Imam Abu al-Hasan and his student, and what he found concerning the radiance of graves during قيام الليل (night prayers)?

There is no legal (Shar'i) evidence in the Qur'an or Sunnah (definition) that houses where night prayers (Qiyam (definition) al-Layl) are performed emit a light seen by the inhabitants of the heavens, or that angels see the light of houses illuminated by the prayers of their occupants. What has been narrated from Ka'b al-Ahbar and Ibn al-Hajj regarding this matter is not reliable; it is either disconnected in its chain of narration (munqati' al-sanad) or not a legal proof (hujjah shar'iyyah), and Ka'b al-Ahbar transmits from the People of the Book.

Prayer is a light for the servant, especially the recitation of the Qur'an within it, as indicated by authentic hadiths from the Prophet, peace be upon him. It has been narrated that angels draw near to the worshipper and listen to the Qur'an from him until the angel places his mouth on the worshipper's mouth, and that prayer is light.

All prayer is light, and night prayer is the best of supererogatory acts. However, the details mentioned in the question about angels seeing the light of worshippers' homes and inspecting them are incorrect and without proof. One should not speak about the unseen except with a legal text. Angels attend gatherings of remembrance (dhikr), Qur'an recitation, and prayer; they record deeds and seek forgiveness for the believers. As for what is mentioned about Al-Junayd or Shaqeeq al-Balkhi, these are dreams or sayings, not legal proofs.