Revākhaṇḍa ascribed to the Vāyupurāṇa (RKV) 227.19

227.19

jñātvā śāstravidhānoktaṃ karma kartum ihārhasi /
nāyaṃ loko 'sti na paro na sukhaṃ saṃśayātmanaḥ //

Having understood the action enjoined by the rules of the scriptures, you ought to perform it here;
there is neither this world nor the next, nor happiness, for the one whose mind is full of doubt.