There are so many subtle forms of legalism that try to make the works of man in some way contribute to God pardoning of our sins and declaring of us righteous and acceptable in his sight. Some try to make faith itself a work and then make faith the ground of our justification. Some try to make the works we do by the Spirit the grounds of our justification. So the Confession rightly challenges all these errors from the beginning and asserts that God justifies us by the work of Christ for us which is received by faith alone.
But what about those who say that if we are forgiven and accepted by the work of Christ and his righteousness received by faith alone then we can live however we want or at least not take obedience and holy living too seriously? This is what 11.2 addresses.
-First it asserts that the character of the faith which leads to justification. It is not first of all a faith that works in in love or in obedience. It is a faith that received and rests on Christ and his righteousness.
-But then it makes clear that the faith which receives and rests upon Christ and his righteousness leading to justification is NEVER ALONE in the person justified.
1. It is ever accompanied with all other saving graces. The one who is given the faith that looks to Christ for justification also receives the holy spirit, a new heart, conviction of sin, repentance, the ability to turn from sin and walk in obedience to the Lord (albeit imperfectly).
2. The faith itself is never a faith that merely receives and rests. It is a living not a dead faith and so is active working by love. It works to obey the commandments of God which are summarized as, “Love the Lord your God with all your heart, soul, mind and strength, and your neighbor as yourself.”
A truly biblical view of salvation then and only a truly biblical view can BOTH assert that our works in no way contribute to our salvation nor could they ever do so AND our works are necessary in the life of a believer. No one should be confident that they are justified by God if they are trusting in whole or in part on their works rather than the work of Christ to make them acceptable to God. No one should be confident that they are justified by God if they are professing to trust in Christ for their salvation but are not living a life of repentance, active faith, and obedience.
Westminster Confession 11.2
II. Faith, thus receiving and resting on Christ and His righteousness, is the alone instrument of justification: yet is it not alone in the person justified, but is ever accompanied with all other saving graces, and is no dead faith, but works by love.
 JOH 1:12
But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name: ROM 3:28
Therefore we conclude that a man is justified by faith without the deeds of the law. ROM 5:1 Therefore being justified by faith, we have peace with God through our Lord Jesus Christ.
 JAM 2:17 Even so faith, if it hath not works, is dead, being alone. 22 Seest thou how faith wrought with his works, and by works was faith made perfect? 26 For as the body without the spirit is dead, so faith without works is dead also. GAL 5:6 For in Jesus Christ neither circumcision availeth anything, nor uncircumcision; but faith which worketh by love.