In plain words
Whatever is offered, given, practiced as tapas, or done without faith is called ‘Asat,’ Partha; it is of no avail after death, nor here.
Word for word
What is offered, given, [what] tapas [is] undergone, and [what is] done without śraddhā, is called 'Asat', O Pārtha; and it [is] not [of avail] after death, nor also here.
अश्रद्धया हुतं दत्तं तपस्तप्तं कृतं च यत्असदित्युच्यते पार्थ न च तत् प्रेत्य नो इह
Other commentaries
The commentators
▸Bhagavadgītābhāṣyam
तत्र च सर्वत्र श्रद्धाप्रधानतया सर्वं सम्पाद्यते यस्मात् , तस्मात् —
अश्रद्धया हुतं हवनं कृतम् , अश्रद्धया दत्तं ब्राह्मणेभ्यः, अश्रद्धया तपः तप्तम् अनुष्ठितम् , तथा अश्रद्धयैव कृतं यत् स्तुतिनमस्कारादि, तत् सर्वम् असत् इति उच्यते, मत्प्राप्तिसाधनमार्गबाह्यत्वात् पार्थ । न च तत् बहुलायासमपि प्रेत्य फलाय नो अपि इहार्थम् , साधुभिः निन्दितत्वात् इति ॥ २८ ॥
In plain words
And in all of this, everywhere, it is faith -- faith above all -- that makes everything come together; and because that is so --
An oblation poured without faith, a gift given to brahmins without faith, austerity undergone without faith — and in just the same way, any praise or salutation offered without faith alone: none of it is real, Pārtha. It falls outside the one path that actually leads to Me. However much effort went into it, it earns nothing — not in the world to come, not even here. The good see straight through it, and that alone is reason enough for its condemnation.
Close to the Sanskrit
And there, everywhere, since everything is accomplished by faith being the predominant factor, therefore --
By faithlessness, the oblation offered, the giving to brahmins done, the austerity practiced and undertaken by faithlessness; likewise, whatever praise, salutation, and so on was done by faithlessness alone — all that is called unreal, O Pārtha, because of being outside the path that is the means to attaining Me. And that, even though of great exertion, is for fruit neither after death nor even here for a purpose, because of being censured by the good.