Holiness in this life is absolutely necessary to salvation.

Be sure to seek for holiness of heart and life only in due order, where God has placed it, after union with Christ, justification and the gift of the Holy Ghost and, in that order, seek it earnestly by faith as a very necessary part of your salvation. I think enough has been said already to show in what order God brings us to the practice of the moral law. He makes us first to be in Christ by faith, as branches in a vine, that we may bring forth much fruit. He first cleanses us from dead works by justification, that we serve the living God. He makes us first to live in the Spirit, and then to walk in the Spirit (Gal. 5:25). This is the order prescribed in the gospel, which is the power of God to salvation, though the law prescribes a quite contrary method, that we should first perform its commands. Look at the advantages you have for the attainment of holiness by this order. You have the advantage of the love of God manifested toward you, in forgiving your sins and receiving you into favor. He gives you the Spirit of adoption and the hope of His Glory. He persuades and constrains you to truly love God. The love of God is shed abroad in your heart by the Holy Spirit which is given unto you. The Lord your God will circumcise your heart, to love the Lord your God with all your heart, and with all your soul, that you may live You have the help of His Spirit to incline you powerfully and to strengthen you for the performance in all holiness. You are given exceeding great and precious promises, that by these you might be partakers of the divine nature, having escaped the corruption that is in the world through lust. Holiness is a very necessary part of salvation that is received by faith in Christ. True salvation must include the complete and total freedom from our sinful, corrupt, and rebellious nature. Without holiness of heart, salvation is not really possible. There multitudes of people who harden their hearts to sin by attempting to trust in Christ for an imaginary salvation that does not consist in true holiness of heart, but only the forgiveness of sin and the escape from eternal punishment. The only way to expose this deception is to show that no person can really trust in Christ for true salvation except they trust Him for holiness of heart. These people really do not want true salvation if they do not desire to be made holy and righteous in their hearts and lives. The plain fact is without holiness of heart salvation is IMPOSSIBLE. It is impossible to be truly saved yet remain living in our sinful, corrupt, and rebellious nature. Holiness must be included in salvation because if Christ has not washed you from the filth of your sins then you have no part of Him. True gospel faith makes us come to Christ with a thirsty appetite, that we may drink of living water, even of His sanctifying Spirit (John 7:37,38), and cry out earnestly to save us, not only from hell, but from sin, saying, Teach me to do Your will; Your Spirit is good (Ps. 143:10). Turn me, and I shall be turned: (Jer. 31:18); Create in me a clean heart, O God; and renew a right Spirit within me (Ps. 51:10). This is the way by which the doctrine of salvation by grace necessitates us to holiness of life, by compelling us to seek for it by faith in Christ as a substantial part of that salvation which is freely given us through Christ. Holiness in this life is absolutely necessary to salvation, not only as a means to the end, but by a honorable kind of necessity, as part of the end itself. But do not be deceived, those who think that holiness is not part of salvation do not understand what true salvation is, neither do they recognize their rebellion and totally wicked heart. They seem blind to their great evil and crime of sin; and that which they trust on Christ for is but an imagination of their own thoughts, and therefore their trusting is gross presumption and in vain.