Bhagavad Gita · 17.28

अश्रद्धया हुतं दत्तं तपस्तप्तं कृतं च यत्।असदित्युच्यते पार्थ न च तत्प्रेत्य नो इह॥

aśhraddhayā hutaṁ dattaṁ tapas taptaṁ kṛitaṁ cha yat asad ity uchyate pārtha na cha tat pretya no iha

Whatever is offered in sacrifice, given in charity, or performed as austerity without faith — it is called 'Asat' (unreal), O Partha. It is of no value here or hereafter.

— Bhagavad Gita 17.28

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)