Skandapurana 5.167.16

5.167.16

.. śrībrahmovāca .. ..
viśvāmitra pratuṣṭo'smi tapasānena sattama ..
varaṃ varaya bhadraṃ te pradāsyāmyapi durlabham .. 16 ..

Glorious Brahmā said:
“O Viśvāmitra, I am well pleased with this austerity, O best of men!
Choose a boon—may it be well with you—I shall grant it even if hard to attain.”