Chapter 17 · The Three Kinds of Faith · Krishna said
Bhagavad Gita 17.28 — Without faith, it is empty
अश्रद्धया हुतं दत्तं तपस्तप्तं कृतं च यत्। असदित्युच्यते पार्थ न च तत्प्रेत्य नो इह ॥
aśraddhayā hutaṃ dattaṃ tapastaptaṃ kṛtaṃ ca yat | asadityucyate pārtha na ca tatprepya no iha ||
Meaning
O Partha, whatever offering, gift, austerity or act is done without faith is called 'asat'; it brings no good, neither in this world nor in the next.