Bhagavatapurana 6.11.23

6.11.23

traivargikāyāsavighātamasmat patirvidhatte puruṣasya śakra /
tato 'numeyo bhagavatprasādo yo durlabho 'kiñcanagocaro 'nyaiḥ //

23. Our Lord causes obstruction to the labour relating to the Triwarga objects (Dharma, Artha and Kama) in the case of His devotee, O Indra, and from this circumstance is to be inferred that the Lord's grace, which is the lot of disinterested votaries, is not easy to be secured by others.