Bhagavad Gita 7.22

If he worships one form alone with real faith, then his desires shall be fulfilled through that alone; for thus I have ordained.

स तया श्रद्धया युक्तस्तस्याराधनमीहते।
लभते च ततः कामान्मयैव विहितान् हि तान्॥

sa tayā śraddhayā yuktastasyārādhanamīhate|
labhate ca tataḥ kāmānmayaiva vihitān hi tān||

English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).