Look at God's own examples in the Bible. To come into line with the truth and requirements of God's Word is to exercise a living faith; to say you believe when you do not do so is a dead faith. Look at the contrast in these passages below and you have your answer basically. You can likewise contrast every righteous person in the Bible with everyone who claimed to be the Lord's but was actually wicked, and you have many examples of the answer illustrated before your eyes.
James 2:14-26: "14 What doth it profit, my brethren, though a man say he hath faith, and have not works? can faith save him? 15 If a brother or sister be naked, and destitute of daily food,
16 And one of you say unto them, Depart in peace, be ye warmed and filled; notwithstanding ye give them not those things which are needful to the body; what doth it profit? 17 Even so faith, if it hath not works, is dead, being alone. 18 Yea, a man may say, Thou hast faith, and I have works: shew me thy faith without thy works, and I will shew thee my faith by my works. 19 Thou believest that there is one God; thou doest well: the devils also believe, and tremble. 20 But wilt thou know, O vain man, that faith without works is dead? 21 Was not Abraham our father justified by works, when he had offered Isaac his son upon the altar? 22 Seest thou how faith wrought with his works, and by works was faith made perfect? 23 And the scripture was fulfilled which saith, Abraham believed God, and it was imputed unto him for righteousness: and he was called the Friend of God.
24 Ye see then how that by works a man is justified, and not by faith only. 25 Likewise also was not Rahab the harlot justified by works, when she had received the messengers, and had sent them out another way? 26 For as the body without the spirit is dead, so faith without works is dead also."
Romans 1:16-21: "16 For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth; to the Jew first, and also to the Greek. 17 For therein is the righteousness of God revealed from faith to faith: as it is written, The just shall live by faith.
18 For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness; 19 Because that which may be known of God is manifest in them; for God hath shewed it unto them. 20 For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse: 21 Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened."
Luke 6:46-49: "46 And why call ye me, Lord, Lord, and do not the things which I say 47 Whosoever cometh to me, and heareth my sayings, and doeth them, I will shew you to whom he is like: 48 He is like a man which built an house, and digged deep, and laid the foundation on a rock: and when the flood arose, the stream beat vehemently upon that house, and could not shake it: for it was founded upon a rock. 49 But he that heareth, and doeth not, is like a man that without a foundation built an house upon the earth; against which the stream did beat vehemently, and immediately it fell; and the ruin of that house was great."