Revākhaṇḍa ascribed to the Vāyupurāṇa (RKV) 45.24

45.24

īśvara uvāca:
svapne 'pi tridaśāḥ sarve na yoddhavyāḥ kadācana /
asaṃbhāvyaṃ na vaktavyaṃ manaso yanna rocate //

Īśvara said: / 'Even in a dream, all the thirty [gods] are never to be fought. / What is impossible should not be spoken, nor what is not pleasing to the mind.