Srimad Bhagavatam Canto 10, Chapter 40, Text 09

SB 10.40.9

sarva eva yajanti tvam
 sarva-deva-mayesvaram
ye ’py anya-devata-bhakta
 yady apy anya-dhiyah prabho
 
Translation: 
 
But all these people, my Lord, even those who have turned their attention away from You and are worshiping other deities, are actually worshiping You alone, O embodiment of all the demigods.
 
Purport: 
 
The idea here is that even those who worship the demigods are indirectly worshiping the Supreme Lord Visnu. The understanding of such worshipers, however, is imperfect.
Srimad Bhagavatam Canto 10, Chapter 40, Text 08
Srimad Bhagavatam Canto 10, Chapter 40, Text 10