Matt 5:13-16

13 You are the salt of the earth, but if salt has lost its taste (its strength, its quality), how can its saltness be restored? It is not good for anything any longer but to be thrown out and trodden underfoot by men.

14 You are the light of the world. A city set on a hill cannot be hidden.

15 Nor do men light a lamp and put it under a peck measure, but on a lampstand, and it gives light to all in the house.

16 Let your light so shine before men that they may see your moral excellence and your praiseworthy, noble, and good deeds and recognize and honor and praise and glorify your Father Who is in heaven.
AMP

Yesterday, I read this portion of Scripture, and began asking God if maybe I've lost my "saltiness." 

My reason for asking was because the night before, we were out for dinner with some friends and family.  There was something lacking in our conversation and as I look back - God was missing in most of our conversation.  

Then I asked, "How are we the salt of the earth?" 

John 15:12-19

12 This is my commandment, That ye love one another, as I have loved you.
13 Greater love hath no man than this, that a man lay down his life for his friends.
14 Ye are my friends, if ye do whatsoever I command you.
15 Henceforth I call you not servants; for the servant knoweth not what his lord doeth: but I have called you friends; for all things that I have heard of my Father I have made known unto you.
16 Ye have not chosen me, but I have chosen you, and ordained you, that ye should go and bring forth fruit, and that your fruit should remain: that whatsoever ye shall ask of the Father in my name, he may give it you.
17 These things I command you, that ye love one another.
18 If the world hate you, ye know that it hated me before it hated you.
19 If ye were of the world, the world would love his own: but because ye are not of the world , but I have chosen you out of the world, therefore the world hateth you.

I gather from the Scriptures, we are in the world but not of it.  We are lights in the world, a city set on a hill CANNOT be hid.  We don't light a lamp and hide it.  Instead, we put it on a stand - to GIVE LIGHT TO EVERYONE IN THE HOUSE.  We don't hide our light - God in us.

We are to be this light/salt/city on a hill.  We've been chosen to be set apart for HIS purposes.  Being set apart for His purposes is true holiness as far as I understand.  Focusing on outward appearances to determine holiness, will cause people to miss the mark.  The Pharisees were clean outwardly, but full of dead men's bones inwardly.

I found these few Scriptures pertaining to being lights in the world and yet not of the world.

John 9:4-5    4 I must work the works of him that sent me, while it is day: the night cometh, when no man can work.  5 As long as I am in the world , I am the light of the world.
KJV

Phil 2:13-15    13 For it is God which worketh in you both to will and to do of his good pleasure.  14 Do all things without murmurings and disputings:  15 That ye may be blameless and harmless, the sons of God, without rebuke, in the midst of a crooked and perverse nation, among whom ye shine as lights in the world ;
KJV

1 John 2:15-17    15 Love not the world, neither the things that are in the world . If any man love the world, the love of the Father is not in him.  16 For all that is in the world , the lust of the flesh, and the lust of the eyes, and the pride of life, is not of the Father, but is of the world.  17 And the world passeth away, and the lust thereof: but he that doeth the will of God abideth for ever.
KJV

1 Peter 2:11-12     11 Dear friends, I urge you, as aliens and strangers in the world , to abstain from sinful desires, which war against your soul. 12 Live such good lives among the pagans that, though they accuse you of doing wrong, they may see your good deeds and glorify God on the day he visits us.
NIV

I'm pretty convinced that being salt and light is being separated "unmistakably" from the world.  The world is the lust of the flesh, and the lust of the eyes, and the pride of life.  These things are not of the Father, but of the world.  

The type of separation I believe the Scripture is supporting is doing the Father's works, bringing forth fruit of the Spirit - LOVE being the greatest.  This would be separated by works, but also in purpose.

Gal 5:16-25     16 This I say then, Walk in the Spirit, and ye shall not fulfil the lust of the flesh.  17 For the flesh lusteth against the Spirit, and the Spirit against the flesh: and these are contrary the one to the other: so that ye cannot do the things that ye would.  18 But if ye be led of the Spirit, ye are not under the law.  19 Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness,  20 Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies,  21 Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God.  22 But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith,  23 Meekness, temperance: against such there is no law.  24 And they that are Christ's have crucified the flesh with the affections and lusts.  25 If we live in the Spirit, let us also walk in the Spirit.
KJV

We must wholly depend and lean on Him, our faith is in Him - not in our own works.  Without God we can do NOTHING.  That's why we walk in the Spirit, our flesh will only bring us under the law of sin.

Rom 7:18-8:9

18 For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not.  19 For the good that I would I do not: but the evil which I would not, that I do.  20 Now if I do that I would not, it is no more I that do it, but sin that dwelleth in me.  21 I find then a law, that, when I would do good, evil is present with me.  22 For I delight in the law of God after the inward man:  23 But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members.  24 O wretched man that I am! who shall deliver me from the body of this death?  25 I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin.

8:1 There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.  2 For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.  3 For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh:  4 That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit.  5 For they that are after the flesh do mind the things of the flesh; but they that are after the Spirit the things of the Spirit.  6 For to be carnally minded is death; but to be spiritually minded is life and peace.  7 Because the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be.  8 So then they that are in the flesh cannot please God.  9 But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his.

KJV