Abu Khalid Kabuli narrates – I asked Abu Jafar (a.s.) concerning the words of Allah:
“Therefore believe in Allah and His Messenger and in the Light which we have sent down…” (Surah Taghaabun (64):8)

He said: ‘O Abu Khalid! The Light, by Allah, is the Light of the Imams from the Household of Muhammad (s.a.w.s.) till the Day of Resurrection. They, by Allah, are the Lights which Allah has sent down, and they, by Allah, are the Lights of Allah in the heavens and on the earth.”
Al-Kaafi v 1 p 194