This verse (chaupai) is from the Balakanda chapter of Shri Ramcharitmanas.
सुमन पाइ मुनि पूजा कीन्ही। पुनि असीस दुहु भाइन्ह दीन्ही॥ सुफल मनोरथ होहुँ तुम्हारे। रामु लखनु सुनि भय सुखारे॥
This verse (chaupai) is Vishwamitra's blessing in Balakanda, given after receiving flowers from Pushpawatika.
Meaning : Receiving the flowers, the sage performed the worship. Then, he blessed both brothers, saying, "May your desires be fulfilled." Hearing this, Ram and Lakshman felt joyful.