Midrasz do Izajasza 50:10

Rabin b. R. Ada in the name of R. Isaac said: "Whoever frequents the synagogue [daily] and misses one day, the Holy One, praised be He! inquires about him; for it is written (Is. 50, 10.) Who is among you, that feareth the Lord, that hearkeneth to the voice of His servant? Though he has walked in darkness and had no light, let him trust in the name of the Lord; i.e., if he went to perform a meritorious deed [and was therefore absent from synagogue] there will be light unto him; but if his absence is due to personal business, then there will be no light unto him for he should have placed his trust in God." R. Jochanan said: When the Holy One, praised be He! enters the synagogue and does not find ten [men] present, His anger is immediately stirred, as it is said (Is. 50, 2.) Why did I come and no man was there, did I call with none to answer."