Salvation is not by works of merit per Eph 2:8-9 but salvation is by obedience to God's will (Rom 6:16; Heb 5:9; Rom 10:9-10; Acts 2:38; etc). And obedience to God's will is never called a work of merit for they are two completely different things.
A distinction without a difference. We are not saved by works in general (Romans 3:24-28; 4:5-6; 11:6; Ephesians 2:8,9; Titus 3:5; 2 Timothy 1:9) so your "not saved by works of merit, but saved by works of obedience" argument is bogus. Roman Catholics make this same argument as well in a desperate attempt to "get around" the fact that man is saved by grace through faith and NOT BY WORKS.
Romans 6:16 clarifies that we are either
servants of sin unto death (descriptive of unbelievers) or
servants of obedience unto righteousness (descriptive of believers). Romans 6:18 says
having been set free from sin, we have become slaves of righteousness. Nothing here about accomplishing multiple acts of obedience/works in order to become righteous according to your eisegesis.
In regards to Hebrews 5:9, who is it that obeys Him? The saved or the lost? I have often heard works-salvationists use this verse to try and support salvation by works. Only
believers have obeyed Him by
choosing to believe the gospel (Romans 1:16)
in order to become saved, and
only believers obey Him after they have been saved through faith by practicing righteousness and not sin. (1 John 3:9,10).
In either sense, only believers obey Him.
Unbelievers
have not obeyed Him by
refusing to believe the gospel (Romans 10:16) and without faith its impossible to please God (Hebrews 11:6), so unbelievers do not obey Him no matter how much "so-called" obedience that they attempt to conjure up through the flesh in a vain effort to receive salvation based on their works.
So in either sense, unbelievers do not obey Him
In Romans 10:9-10, confessing with our mouth that Jesus is Lord and believing in our heart that God raised Him from the dead are not two separate steps to salvation, but are
chronologically together. Romans 10:8 But what does it say? “The word is near you,
in your mouth and in your heart” TOGETHER (that is, the
word of faith which we preach). Confession is an expression of faith by the Holy Spirit (1 Corinthians 12:3) and not a work for salvation.
In Acts 2:38, "for the remission of sins" does not refer back to both clauses, "you all repent" and "each one of you be baptized," but refers only to the first. Peter is saying "repent unto the remission of your sins," the same as in Acts 3:19. The clause "each one of you be baptized" is parenthetical. This is exactly what Acts 3:19 teaches except that Peter omits the parenthesis.
*Also compare the fact that these Gentiles in Acts 10:45 received
the gift of the Holy Spirit (compare with Acts 2:38 -
the gift of the Holy Spirit) and this was BEFORE water baptism (Acts 10:47).
In Acts 10:43 we read
..whoever believes in Him receives remission of sins. Again, these Gentiles received
the gift of the Holy Spirit - Acts 10:45 -
when they believed on the Lord Jesus Christ - Acts 11:17 - (compare with Acts 16:31 -
Believe on the Lord Jesus Christ and you will be saved) BEFORE water baptism - Acts 10:47. This is referred to as
repentance unto life - Acts 11:18.
*So the only logical conclusion
when properly harmonizing Scripture with Scripture is that faith in Jesus Christ "implied in genuine repentance" (rather than water baptism) brings the remission of sins and the gift of the Holy Spirit (Luke 24:47; Acts 2:38; 3:19; 5:31; 10:43-47; 11:17,18; 15:8,9; 16:31; 26:18). *Perfect Harmony*
There is a difference between obeying God's will IN ORDER TO BECOME SAVED: John 6:40 - For
my Father’s will is that everyone who looks to the Son and
believes in him shall have eternal life, and I will raise them up at the last day.
AND
Obeying God's will AFTER WE HAVE BEEN SAVED: 1 Thessalonians 5:14 - Now we
exhort you, brethren, warn those who are unruly, comfort the fainthearted, uphold the weak, be patient with all. 15 See that no one renders evil for evil to anyone, but always pursue what is good both for yourselves and for all. 16 Rejoice always, 17 pray without ceasing, 18 in everything give thanks; for
this is the will of God in Christ Jesus for you.