“τῇ γὰρ χάριτί ἐστε σεσῳσμένοι διὰ τῆς πίστεως καὶ τοῦτο οὐκ ἐξ ὑμῶν θεοῦ τὸ δῶρον οὐκ ἐξ ἔργων ἵνα μή τις καυχήσηται.”
Calvinists like Piper have typically used Eph. 2:8-9 to teach that faith was the gift of God, though even Calvin admitted that this verse was not saying that.
However, “τοῦτο” [that] is a neuter demonstrative pronoun. But “πίστεως” [faith] is feminine. This is vital because when Greek demonstratives modify nouns, they will agree with the noun in gender, …number and case. And so “τοῦτο” [that] is not in reference to the “πίστεως” [faith] plain and simple.
“πίστεως” [faith] may be the closest to “τοῦτο” [that] but that is not how you determine its reference in a Greek sentence. The endings of the words that are how you do that.
The gift cannot be “χάριτί” [grace] as that is feminine also. It is gracious for God to give a gift so that grace is the basis of the gift, but the grace itself is not the gift. A person may give you a gift out of their generosity, but they do not give you the gift of generosity.
And while “σῴζω” [saved] is a verb, “τοῦτο” applies to the whole thought Paul was expressing about salvation, with the noun being elliptical. So it would read, “For by grace through faith are ye saved, and that not of yourselves, it is a gift of God lest any man should boast.”
In plain English, Ephesians 2:8-9 is teaching that salvation is the gift of God.
And the fact that the command to “believe” “πιστεύω” is in the imperative mood and active voice also shows that it is a choice of the will that God is commanding men to make. This is also supported by the fact that God rebukes and punishes men if they don’t believe, showing the volitional and avoidable nature of unbelief.
A Greek Exposition of Acts 13:48 – “as many as were ordained to eternal life believed.” Jesse Morrell