Calvinist’s claim that the words ”that not of yourselves” refers to “faith” and the “gift of God” refers to it also. They believe that man does not have free will to have faith in Jesus Christ so the Holy Spirit gives those who God chooses to save to be the recipient of the gift of faith.

Others claim that the words ”that not of yourselves” refer to “salvation” and the “gift of God” refers to it also. The grammar, however, resolves the issue.

Ephesians 2:8-9 For by grace [noun dative sing. fem. of charis] you have been saved [participle perfect pass. nominative masculine plural of sozo] through faith [genitive sing. of pistis]; and that [pronoun nominative singular of houtos] not of your- selves, it is the gift [noun nominative neuter of doron] of God; 9) not as a result of works, so that no one may boast.
In Gr. nouns have five cases that show how nouns function in a sentence. The nominative case indicates the subject of the sentence.
Notice that “faith” is not in the nominative case, but is in the genitive case which usually indicates possession of something. Ex. “the blood of Christ” – of Christ would be in the genitive case to show that the blood belongs to Christ. It doesn’t relate to the subject of a sentence.

Since those in the reformed camp believe that man does not have the ability to have faith in Jesus Christ, God has to give them the faith to believe (called irresistible grace). But in Eph. 2:8, the phrase “that (nom. case) not of yourselves” does not refer “faith” (gen. case) but to salvation (nom. case).
Also, the phrase. “the gift (nom. case) of God” does not refer “faith” (gen. case) but to salvation (nom. case).