Those who worship the demigods receive reciprocation from the demigods in a way just corresponding to the offering. The demigods are attendants of karma, like a person’s shadow, but sādhus are actually merciful to the fallen.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
भजन्ति ये यथा देवान् देवा अपि तथैव तान् । छायेव कर्मसचिवाः साधवो दीनवत्सलाः
bhajanti ye yathā devān devā api tathaiva tān | chāyeva karmasacivāḥ sādhavo dīnavatsalāḥ
SB 11.2.6