SB 9.1.18

yūyaṁ brahma-vido yuktās
 tapasā dagdha-kilbiṣāḥ
kutaḥ saṅkalpa-vaiṣamyam
 anṛtaṁ vibudheṣv iva
Synonyms: 
yūyam — of all you; brahma-vidaḥ — completely in awareness of the Absolute Truth; yuktāḥ — self-controlled and well balanced; tapasā — by dint of austerity and penances; dagdha-kilbiṣāḥ — all kinds of material contamination having been burnt out; kutaḥ — then how; saṅkalpa-vaiṣamyam — discrepancy in the matter of determination; anṛtam — false promise, false statement; vibudheṣu — in the society of the demigods; iva — or.
Translation: 
You are all self-controlled, well balanced in mind, and aware of the Absolute Truth. And because of austerities and penances you are completely cleansed of all material contamination. Your words, like those of the demigods, are never baffled. Then how is it possible that your determination has failed?
Purport: 

We have learned from many Vedic literatures that a benediction or curse given by the demigods never proves false. By performing austerities and penances, by controlling the senses and mind, and by achieving full knowledge of the Absolute Truth, one is fully cleansed of material contamination. Then one’s words and blessings, like those of the demigods, are never a failure.