What Scriptures are used to justify the belief that Christians of Denominations other than a specific one will be rejected by God? In my studies of the Bible I have never found times when God has rejected the worship of anyone who worshipped him in sincerity.
The only restrictions to worship other than worshipping in holiness as far as I have been able to find is in:

Again I say unto you, That if two of you shall agree on earth as touching any thing that they shall ask, it shall be done for them of my Father which is in heaven. For where two or three are gathered together in my name, there am I in the midst of them. (Matthew 18:19-20, KJV)

And David in Psalms decreed:

Who shall ascend into the hill of the Lord? or who shall stand in his holy place? He that hath clean hands, and a pure heart; who hath not lifted up his soul unto vanity, nor sworn deceitfully.  He shall receive the blessing from the Lord, and righteousness from the God of his salvation. This [is] the generation of them that seek him, that seek thy face, O Jacob. Selah. (Psalms 24:3-6, KJV)
Give unto the Lord the glory due unto his name; worship the Lord in the beauty of holiness. (Psalms 29:2, KJV)

And in Hosea it says:

For I desired mercy, and not sacrifice; and the knowledge of God more than burnt offerings. (Hosea 6:6, KJV)

As far as I am able to determine God  does not seem to be concerned except that we humbly worship him in righteousness.
So for those who do believe that God only accepts a single denomination, what scriptural passages do they use to back it up?
The first scripture that occurs to me in this connection is Galatians 1:8, where St. Paul writes: "But though we, or an angel from heaven, preach a gospel to you besides that which we have preached to you, let him be anathema."