Moving on, we come to q&a #35:
Q. 35. What is sanctification?
A. Sanctification is the work of God’s free grace, whereby we are renewed in the whole man after the image of God, and are enabled more and mare to die unto sin, and live unto righteousness.
From Thomas Watson's Body of Divinity we read:
How may sanctification be attained?
(1) Be conversant in the word of God. 'Sanctify them through thy truth' (John 17:17). The word is both a glass to show us the spots of our soul, and a laver to wash them away. The word has a transforming virtue in it; it irradiates the mind, and consecrates the heart.
(2) Get faith in Christ's blood. 'Having purified their hearts by faith' (Acts 15:9). She in the gospel who touched the hem of Christ's garment was healed. A touch of faith purifies. Nothing can have a greater force upon the heart, to sanctify it, than faith. If I believe Christ and his merits are mine, how can I sin against him? Justifying faith does that in a spiritual sense which miraculous faith does, it removes mountains, the mountains of pride, lust, envy. Faith and the love of sin are inconsistent.
(3) Breathe after the Spirit. It is called 'the sanctification of the Spirit (2 Thess. 2:13). The Spirit sanctifies the heart, as lightning purifies the air, and as fire refines metals. Omne agens generat sibi simile. [The Spirit at work generates its own likeness everywhere.] The Spirit stamps the impression of its own sanctity upon the heart, as the seal prints its likeness upon the wax. The Spirit of God in a man perfumes him with holiness, and makes his heart a map of heaven.
(4) Associate with sanctified persons. They may, by their counsel, prayers, and holy example, be a means to make you holy. As the communion of saints is in our creed, so it should be in our company. 'He that walketh with the wise shall be wise' (Prov. 13:20). Association begets assimilation.
(5) Pray for sanctification. Job propounds a question. 'Who can bring a clean thing out of an unclean' (Job 14:4). God can do it. Out of an unholy heart he can produce grace. Oh! make David's prayer your own, 'Create in me a clean heart, O God' (Ps. 51:10). Lay thy heart before the Lord, and say, Lord, my unsanctified heart pollutes all it touches. I am not fit to live with such a heart, for I cannot honour thee; nor die with such a heart, for I cannot see thee. Oh create in me a new heart! Lord, consecrate my heart, and make it thy temple, and thy praises shall be sung there for ever.
Use three: Has God brought a clean thing out of an unclean? has he sanctified you? Wear this jewel of sanctification with thankfulness. 'Giving thanks to the Father, who hath made us meet for the inheritance' (Col. 1:12). Christian, thou couldst defile thyself, but not sanctify thyself; but God has done it, he has not only chained up sin, but changed thy nature, and made thee as a king's daughter, all glorious within. He has put upon thee the breastplate of holiness, which, though it may be shot at, can never be shot through. Are there any here that are sanctified? God has done more for you than millions, who may be illumined, but are not sanctified. He has done more for you than if he had made you the sons of princes, and caused you to ride upon the high places of the earth. Are you sanctified? Heaven is begun in you; for happiness is nothing but the quintessence of holiness. Oh, how thankful should you be to God! Do as that blind man in the gospel did after he had received his sight, who 'followed Christ, glorifying God' (Luke 18:43). Make heaven ring with God's praises.
Christ’s prayer is, “Sanctify them through thy truth.” The more truth you believe, the more sanctified you will be. The operation of truth upon the mind is to separate a man from the world unto the service of God. Just in proportion as truth is given up, worldliness and frivolity are sure to prevail. - C.H. Spurgeon