Well actually you should go through Romans 10 to establish that FACT.
And it is not "our act of obedience" but "obedience to the Gospel" (repentance toward God and faith toward our Lord Jesus Christ -- Acts 20:21).
ROMANS 10
1. PAUL PRAYS FOR THE SALVATION OF ALL ISRAEL (NO UNCONDITIONAL ELECTION FOR SALVATION)
1 Brethren, my heart's desire and prayer to God for Israel is, that they might be saved.
2. THE JEWS HAVE A ZEAL BUT NOT ACCORDING TO THE GOSPEL
2 For I bear them record that they have a zeal of God, but not according to knowledge.
3. THEY FORGET THAT GOD IMPUTES RIGHTEOUSNESS TO THE BELIEVER
3 For they being ignorant of God's righteousness, and going about to establish their own righteousness, have not submitted themselves unto the righteousness of God.
4. RIGHTEOUSNESS IS IMPUTED TO THOSE WHO BELIEVE ON CHRIST
4 For Christ is the end of the law for righteousness to every one that believeth.
5. RIGHTEOUSNESS ACCORDING TO THE LAW IS NOT OF FAITH
5 For Moses describeth the righteousness which is of the law, That the man which doeth those things shall live by them.
6. IMPUTED RIGHTEOUSNESS IS BY FAITH IN GOD AND CHRIST
6 But the righteousness which is of faith speaketh on this wise, Say not in thine heart, Who shall ascend into heaven? (that is, to bring Christ down from above). 7 Or, Who shall descend into the deep? (that is, to bring up Christ again from the dead). 8 But what saith it? The word is nigh thee, even in thy mouth, and in thy heart: that is, the word of faith, which we preach;
7. HERE IS HOW SINNERS ARE SAVED
9 That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved. 10 For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.
8. THIS IS OBEDIENCE TO THE GOSPEL
11 For the scripture saith, Whosoever believeth on him shall not be ashamed.
9. SALVATION IS FOR ALL WITHOUT EXCEPTION ("WHOSOEVER")
12 For there is no difference between the Jew and the Greek: for the same Lord over all is rich unto all that call upon him. 13 For whosoever shall call upon the name of the Lord shall be saved.
THE PREACHING OF THE GOSPEL IS NECESSARY FOR SALVATION
14 How then shall they call on him in whom they have not believed? and how shall they believe in him of whom they have not heard? and how shall they hear without a preacher?
PREACHERS ARE SENT BY GOD TO PREACH THE GOSPEL
15 And how shall they preach, except they be sent? as it is written, How beautiful are the feet of them that preach the gospel of peace, and bring glad tidings of good things!
OBEDIENCE TO THE GOSPEL IS A CONSCIOUS DECISION (FREE WILL EVIDENT)
16 But they have not all obeyed the gospel. For Esaias saith, Lord, who hath believed our report?
SAVING FAITH IS GENERATED BY THE GOSPEL (THE WORD OF GOD)
17 So then faith cometh by hearing, and hearing by the word of God.
ISRAEL GENERALLY FAILED TO OBEY THE GOSPEL
18 But I say, Have they not heard? Yes verily, their sound went into all the earth, and their words unto the ends of the world. 19 But I say, Did not Israel know? First Moses saith, I will provoke you to jealousy by them that are no people, and by a foolish nation I will anger you. 20 But Esaias is very bold, and saith, I was found of them that sought me not; I was made manifest unto them that asked not after me. 21 But to Israel he saith, All day long I have stretched forth my hands unto a disobedient and gainsaying people.