If they shall fall away - Και παραπεσοντας And having fallen away. I can express my own mind on this translation nearly in the words of Dr. Macknight: "The participles φωτισθεντας, who were enlightened, γευσαμενους, have tasted, and γενηθεντας, were made partakers, being aorists, are properly rendered by our translators in the past time; wherefore, παραπεσοντας, being an aorist, ought likewise to have been translated in the past time, Have fallen away. Nevertheless, our translators, following Beza, who without any authority from ancient MSS. has inserted in his version the word si, if, have rendered this clause, If they fall away, that this text might not appear to contradict the doctrine of the perseverance of the saints. But as no translator should take upon him to add to or alter the Scriptures, for the sake of any favourite doctrine, I have translated παραπεσοντας in the past time, have fallen away, according to the true import of the word, as standing in connection with the other aorists in the preceding verses."

Dr. Macknight was a Calvinist, and he was a thorough scholar and an honest man; but, professing to give a translation of the epistle, he consulted not his creed but his candour. Had our translators, who were excellent and learned men, leaned less to their own peculiar creed in the present authorized version, the Church of Christ in this country would not have been agitated and torn as it has been with polemical divinity.

It appears from this, whatever sentiment may gain or lose by it, that there is a fearful possibility of falling away from the grace of God; and if this scripture did not say so, there are many that do say so. And were there no scripture express on this subject, the nature of the present state of man, which is a state of probation or trial, must necessarily imply it. Let him who most assuredly standeth, take heed lest he fall.

To renew them again unto repentance - As repentance is the first step that a sinner must take in order to return to God, and as sorrow for sin must be useless in itself unless there be a proper sacrificial offering, these having rejected the only available sacrifice, their repentance for sin, had they any, would be nugatory, and their salvation impossible on this simple account; and this is the very reason which the apostle immediately subjoins: -

Seeing they crucify to themselves the Son of God - They reject him on the ground that he was an impostor, and justly put to death. And thus they are said to crucify him to themselves - to do that in their present apostasy which the Jews did; and they show thereby that, had they been present when he was crucified, they would have joined with his murderers.

And put him to an open shame - Παραδειγματιζοντας· And have made him a public example; or, crucifying unto themselves and making the Son of God a public example. That is, they show openly that they judge Jesus Christ to have been worthy of the death which he suffered, and was justly made a public example by being crucified. This shows that it is final apostasy, by the total rejection of the Gospel, and blasphemy of the Savior of men, that the apostle has in view. See the note on Hebrews 6:4 (note).

to renew. See on ver.

Hebrews 6:4 For it is impossible for those who were once enlightened, and have tasted of the heavenly gift...

Psalm 51:10 Create in me a clean heart, O God; and renew a right spirit within me.

Isaiah 1:28 And the destruction of the transgressors and of the sinners shall be together, and they that forsake the LORD shall be consumed.

2 Timothy 2:25 In meekness instructing those that oppose themselves; if God peradventure will give them repentance to the acknowledging of the truth;

they crucify.

Hebrews 10:29 Of how much sorer punishment, suppose you, shall he be thought worthy, who has trodden under foot the Son of God...

Zechariah 12:10 And I will pour on the house of David, and on the inhabitants of Jerusalem, the spirit of grace and of supplications...

*etc:

Matthew 23:31,32 Why you be witnesses to yourselves, that you are the children of them which killed the prophets...

Luke 11:48 Truly you bear witness that you allow the deeds of your fathers: for they indeed killed them, and you build their sepulchers.

an open.

Hebrews 12:2 Looking to Jesus the author and finisher of our faith; who for the joy that was set before him endured the cross, despising the shame...

Matthew 27:38-44 Then were there two thieves crucified with him, one on the right hand, and another on the left...

Mark 15:29-32 And they that passed by railed on him, wagging their heads, and saying, Ah, you that destroy the temple, and build it in three days...

Luke 23:35-39 And the people stood beholding. And the rulers also with them derided him, saying, He saved others; let him save himself...

Analysis Necessary.
"Let us go on unto perfection; not laying again the foundation." --Heb. vi. 1. To systematize the work of the Holy Spirit in individuals, we must first consider their spiritual condition before conversion. Misunderstanding concerning this leads to error and confusion. It causes the various operations of the Holy Spirit to be confounded, so that the same terms are used to designate different things. And this confuses one's own thought, and leads others astray. This is most seriously apparent in ministers …
Abraham Kuyper—The Work of the Holy Spirit

The Joint Heirs and their Divine Portion
I would invite you, my brethren in Christ Jesus, this morning, to do three things; first, let us consider the terms of the will--"joint heirs with Christ;" secondly, let us go forth and view the estates--what it is of which we are joint heirs; and when we have done so, let us proceed at once to administer, for God hath made his children administrators as web as heirs. I. First, then, there is A LEGAL TERM IN THE WILL UPON WHICH THE WHOLE MATTER WILL HINGE. We are called "joint heirs with Christ"--what …
Charles Haddon Spurgeon—Spurgeon's Sermons Volume 7: 1861

Inconsideration Deplored. Rev. Joshua Priestley.
"And they consider not in their hearts that I remember all their wickedness."--HOSEA vii. 2. Is it possible for any man to conceive of truths more fitted to arrest the attention and impress the heart than are those contained in this volume? It has been said that if a blank book had been put into our hands, and every one of us had been asked to put into it the promises we should like to find there, we could not have employed language so explicit, so expressive, and so suited to all our varied wants, …
Knowles King—The Wesleyan Methodist Pulpit in Malvern