|Dr. Martin Luther, Reformer|
If Salvation is attained through faith alone, and if works of charity are completely unnecessary and superfluous, why then does the Bible exhort Christians to be holy in all their conduct (1 Peter 1:15-16)? What for if it doesn't have any bearing to one's eternal destiny?
First of all, it is not true that doing service to God or performing acts of charity are completely unnecessary and superfluous. According to Jesus Christ, it is through our obedience to God's law that we evince our love for Him (John 14:21, 23). However, these works won't save us because no amount of human works can suffice to reach God's glorious standard of perfection (Matthew 5:48; Romans 3:20, 23; James 2:10; Revelation 21:27). The psalmist writes, "If you, O LORD, should mark iniquities, O Lord, who could stand?" (Psalms 130:3); and again, "Enter not into judgment with your servant, for no one living is righteous before you" (Psalms 143:2; cf. Romans 3:10).
God's simple plan of Salvation is that everyone who completely rests in Christ alone for Salvation should be counted as righteous in His sight freely as a gift (Romans 3:24-25, 4:1-6, 5:19; 2 Corinthians 5:21; Galatians 4:4-5; Ephesians 2:8-9). Good works will follow after a justified person as an outward evidence of his genuine conversion in Christ (Ephesians 2:10; Titus 3:6-8; James 2:21-23), but these do not contribute to the attainment or maintenance of the grace of justification once received through faith. Let me explain further.
Common sense tells us that we obey our earthly parents not because we want them to be our parents, but because they are our parents. The same is true with Christians who strive to please their Savior in every way they can, not in order that they may be saved, but because they are already saved. The child of God serves his Father in heaven, not because he wants to be God's child. He is already a child of God; a new creation in Christ (2 Corinthians 5:17); a heir of God's promises; that's why he serves his heavenly Father. St. John the apostle writes:
"We know that everyone who has been born of God does not keep on sinning, but he who was born of God protects him, and the evil one does not touch him." (1 John 5:18)In other words, Christians don't work in order to get saved. They diligently work for righteousness because they are already saved, having the Holy Spirit dwelling in their hearts who produces in them the willingness and power to do what pleases God for His own glory (2 Corinthians 3:18; Romans 8:13-17, 26; Philippians 2:13). Clear enough? Praise the Lord.