Hebrews chapter 10 obviously talks about Christ, the Great High Priest, doing the will of God the Father, v. 9. The Father's will for the Son was clearly revealed in the law and the prophets, consisting of offering His body as a sacrifice, vv. 7 & 5. The Father has never been pleased with simply sacrifices, but requiring first of all obedience; in fact, the Spirit has some harsh words for those who separate sacrifice from obedience, 1 Sa 15:22 ; Hos 6:6 & Mr 12:33 [and from praise, Ps 69:30, 31].
Heb 10:9 quotes Ps 40:7, which is given in the context of v. 6: The pleasing thing to the Lord God has always been, is and will always be doing His will as revealed in His Word.
Heb 10:9, he taketh away the first, that he may establish the second—That is, the sacrifices, to establish the second, that is, the will of God. [Geneva]
Christ's perfect obedience to the Father's will as revealed in the book of the law, v. 1, resulted in the Father's promises to Him being fulfilled:
1) after doing the Father's will in sacrificing His body, the Father set apart—sanctified—His people, v. 10. [See the promise, Zech 13:1, &c.]
2) after doing the Father's will, Christ sat down on the right hand of the Father from where all His enemies will be subdued, as promised to Him by the Father in the Word: When the Son did the Father's will, the Father fulfilled the promise made to the Son, vv. 12, 13—Ps 110:1ff. [See also Mt 22:44 & Heb 1:13.]
3) after doing the Father's will, the Father wrote His laws in the hearts of His people, vv. 16ff. [Jer 31:33, 34.]
4) after doing the Father's will, free access was provided according to the promise, vv. 18ff. [Jer 24:7 ; 32:38 ; Ez 37:27, & Zec 8:8.]
Having established the fact that God the Father fulfilled His promises to the Son because the Son faithfully and fully did the Father's will as revealed in the law, vv. 1 & 7, the Author of Hebrews—God's Spirit—continues. Heb 10:23, the emphasis changes from the sacrificial law to the moral law. Sin is a violation of the law; that is, failure to do the Father's will as revealed in the volume of the book, vv. 7, 26, 1 Jo 3:4.
When and if we fail willfully from His will, the Father is angry. [Willfully speaks of hardness in sin, e.g., maybe saying it does not matter to God nor man.] This statement is given in the context of v. 25: One of the best examples, therefore, of willful sin is folks saying that it does not matter to God about the public assembly: "I can worship God at home just as well as I can in church service around those hypocrites."
The warning continues, v. 28ff: Death was not the result of failure to offer the proper sacrifices, but from violating the moral law given through Moses.
Vv. 32ff., speaks of the things the people endured because of their faith; v. 35 calls for patiently waiting for God to fulfill His promises, and v. 36, tells God's people that God the Father will also fulfill His promises to them as given in His Word, i.e. the Old Testament. Remember, there was no New Testament when Hebrews was written. Thus He will fulfill the promises to them on the same conditions He fulfilled His promises to the Son: FAITHFULLY AND FULLY DOING THE FATHER'S WILL AS REVEALED IN THE WORD OF GOD, v. 9.
Provision made
The Author has dealt with the problem of trying to do the Father's will and failing: He showed that Christ made the sacrifice for sin. The Author has also dealt with the problem of presumption, e.g. "I am a Christian; therefore, God will do it for Christ's sake regardless of whether or not I follow His Word in right living." He points out that presumption only inherits God's promised wrath, not His blessings. The "good" promises of His word are only for those who patiently do the Father's will as revealed in the volume of the book, vv. 35, 36.
V. 38, the Author tells the people that He has just defined faith for all people of all time: Old Testament saints as well as New Testament saints, vv. 35, 36. We must say that vv. 35, 36 define faith better than Heb 11:1. He 11, however, illustrates what the Spirit tells us in 10:35, 36.
V. 39, perdition refers to eternal destruction or damnation. This passage teaches, therefore, that those who truly belong to Christ will be kept faithful to the Father's will as revealed in His Word: Strongly implied is that those who see no need of doing vv. 35, 36, are not saved, and are on the road to destruction.
Chapter 10 clearly defines the faith that inherits the promises of God: It is doing the will of the Heavenly Father as revealed in His Word, primarily in the law, and patiently waiting for the Father to fulfill His promises: It was true of the Old Testament saints; it was true for Christ because v. 7 speaks specifically of Christ doing the Father's will as revealed in the Old Testament law; it is, accordingly, true for the New Testament saints.
Vv. 35, 36, clearly applies for all of God's people of all times, for if Christ inherited the Father's promises to Him by doing the Father's will, it is a most foolish and sinful presumption to think that any man can inherit the promises of God's Word apart from having done the will of God.
Grace, the desire [and the wisdom to know] and the power to do God's will as found in the volume of the book. Thus it is strictly by God's grace that we are able to inherit the promises of God.
There are two promises given in Hebrews 10:
First, do the Father's will as revealed in His word and inherit His promised blessings.
Second, ignore His will as revealed in His word and inherit His promised vengeance against sin.