Matthew 7:21-23
21 Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.
22 Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works?
23 And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.
This passage is very commonly used to teach a works-based Salvation. Alongside Philippians 2:12 and James chapter 2, it is one of the most frequent passages we find ourselves having to deal with in the Free Grace camp, and anyone who has been online for any amount of time engaging in discussions around Salvation will have seen it used in this way.
Therefore, it's important to have a good understanding of what the Lord is saying here, so that we can give clear, concise responses to those who have difficulty with these verses.
For those who believe that you have to behave to get to Heaven, the "will of the Father" in verse 21 is seen as a nondescript commandment to obey everything commanded by God. If you don't obey, to some undefined degree, you will hear Jesus say "I never knew you", and He will send you to Hell. This is how the passage is typically interpreted.
Luckily, this misunderstanding is easy to resolve, because "the will of the Father" is explicitly defined for us elsewhere in the Gospels, and we see that it has a very distinct meaning:
John 6:39-40
39 And this is the Father's will which hath sent me, that of all which he hath given me I should lose nothing, but should raise it up again at the last day.
40 And this is the will of him that sent me, that every one which seeth the Son, and believeth on him, may have everlasting life: and I will raise him up at the last day.
According to the above, "the Father's will", as preached by Jesus Christ, specifically in the Gospels during His ministry, is not just vaguely referring to everything that God has ever commanded mankind. It has to do with God wanting all men to believe in Jesus, and then for all those who believe to "have Everlasting Life", with Jesus losing "nothing" - not a single believer. Salvation by faith alone, and Eternal Security, is the "will of the Father".
We see this echoed later in the Epistles, where we are told that God "will have all men to be saved, and to come unto the knowledge of the truth" (1 Timothy 2:4). The Father's will is for all men to be saved, and elsewhere it is made clear that we are "saved through faith", and "not by works of righteousness which we have done" (Ephesians 2:8-9, Titus 3:5).
This can also be seen elsewhere in the book of Matthew. In Matthew 21, the Lord gives a parable of two sons working in their father's vineyard:
Matthew 21:28-32
28 But what think ye? A certain man had two sons; and he came to the first, and said, Son, go work to day in my vineyard.
29 He answered and said, I will not: but afterward he repented, and went.
30 And he came to the second, and said likewise. And he answered and said, I go, sir: and went not.
31 Whether of them twain did the will of his father? They say unto him, The first. Jesus saith unto them, Verily I say unto you, That the publicans and the harlots go into the kingdom of God before you.
32 For John came unto you in the way of righteousness, and ye believed him not: but the publicans and the harlots believed him: and ye, when ye had seen it, repented not afterward, that ye might believe him.
Here, one son represents the "chief priests and Pharisees" (Matthew 21:45), and unbelieving Jews more generally, whom Christ is preaching at throughout this part of the chapter (Matthew 21:23-27, 21:33-41).
In the parable, one son did "the will of his father", and Christ likens the other son, who didn't do his father's will, to the unbelieving Jews, because they didn't believe John the Baptist's testimony of Christ, nor did they believe Christ himself (Matthew 21:32). Therefore, not doing the "father's will" finds its parallel in unbelief in the Messiah.
On the other hand, if our passage in question from Matthew 7 was teaching that we get to Heaven by doing "God's will" to some unknown degree, in every aspect and facet of our lives, then we would be saved solely by keeping the Law of God, which is Biblically impossible.
Notice in verse 22 that the losts' claim that they are known of Christ is based on their "wonderful works". This betrays an entirely misplaced faith. These people were trusting in their obedience to earn their way into Heaven.
Picture this - you get to the gates of Heaven, and God Almighty says that you can't get in. How would you respond? Would you even dream of bringing up your works?
Absolutely not - I know the testimony of Scripture regarding me - "There is none righteous, no, not one" (Romans 3:10), "all our righteousnesses are as filthy rags" (Isaiah 64:6), "every man at his best state is altogether vanity" (Psalm 39:5). I would only mention Jesus Christ's atonement, and my faith in Him (Philippians 3:9).
These are professing Christians who did not understand the first thing about the Gospel - no one can get to Heaven by their "wonderful works", whether they called Christ "Lord" or not. Every single human being to ever live will eventually call Jesus Christ "Lord" (Philippians 2:9-11, Isaiah 45:23).
Notice that in verse 23, the Lord says to the lost, "I never knew you".
Elsewhere in Scripture, we learn that all believers are in the family of God, because "Whosoever believeth that Jesus is the Christ is born of God" (1 John 5:1), and "ye are all the children of God by faith in Christ Jesus" (Galatians 3:26). Consequently, we are the siblings of Jesus Christ, which is why He is called "the firstborn among many brethren" (Romans 8:29).
Surely, if anyone is "known" of Christ, it would be His siblings, which is why we are explicitly told as believers that we "are known of God" (Galatians 4:9), and "the Lord knoweth them that are his" (2 Timothy 2:19). In the Gospel of John, Christ says that "I am the good shepherd, and know my sheep, and am known of mine" (John 10:14), and then goes on to define His "sheep" as believers (John 10:26). It would be egregiously false, then, if the Lord told any believer that He "never" knew them.
So, Matthew 7:23 is actually a strong proof for the doctrine of "Once Saved, Always Saved", because it shows that if the Lord ever knew you, He will not tell you to "depart" from Him on that day.
It's sad that a passage which actually teaches Salvation by faith alone, and Eternal Security, is so often misused to teach that one must work their way to Heaven.