Hebrews 7:8 is absolutely 
not saying that the practice of tithing was  being followed by the New Testament church at the time the book of  Hebrews was written. It is also 
not talking about a practice of tithing  that is supposed to be in effect permanently, throughout the church age.  The phrase here men that die receive tithes is not talking about  Christian ministers in the church, now or then. 
It is talking about  priests at the temple in Jerusalem. The context bears that out. The he that is being referred to  by the phrase but there he receiveth them is 
Melchizedek, 4000 years  ago, 
not Jesus.
      This verse is incorrectly interpreted by some to say in effect:
And here (in the New Covenant), men that die (our  pastors and other ministers) receive tithes (from born-again  Christians); but there (up in heaven) he (Jesus) (is the one who  actually) is receiving them, of whom it is witnessed that he liveth.
This erroneous interpretation of the verse does not comprehend the  theological argument that is being made in the passage. This  misinterpretation is carelessly taken to be a scriptural proof that  tithing is the will of God and the standard mode of operation in the New  Covenant.
      Objectively interpreted within its context, the verse is actually saying:
And here (in Israel at the time that Hebrews was  written) men (who are priests under the Old Covenant) that (will  eventually) die (and be succeeded by another mortal man after them)  receive tithes (from those who are following the Law of Moses); but  there (2000 years prior, during the time of Abraham in Genesis 14) he  (Melchizedek) receiveth them, of whom it is witnessed that he liveth.
Scholars and theologians debate whether this language referring to  Melchizedek's endless life is literal or symbolic. In either case the  verse 
is not a reference to tithing in the New Covenant. Here men that  die receive tithes is referring to 
Old Covenant priests not to New  Covenant ministers. There he receiveth them is referring to  Melchizedek in Genesis 14:1820, not to Jesus up in heaven now. Nowhere  in the verse is the New Covenant being referred to. This passage is not  teaching that tithing is the way of giving that God has ordained for the  New Covenant.
      Consider some other translations of Hebrews 7:8:
Furthermore, here [in the Levitical priesthood]  tithes are received by men who are subject to death; while there [in the  case of Melchizedek], they are received by one of whom it is testified  that he lives [perpetually]. (The Amplified Bible. Copyright © Zondervan  Publishing House 1965)
And here, on the one hand, men subject to death  are receiving tithes, but there he [Melchisedec] receives them,  concerning whom the testimony is that he is living. (The New Testament:  An Expanded Translation by Kenneth S. Wuest. Copyright © Wm. B. Eerdmans  Publishing Co. 1961)
The he referred to in Hebrews 7:8 is the same he referred to in  verse 6. That he is Melchizedek. That he is not referring to Jesus  in the New Covenant. Melchizedek is the subject of verse 1 and is  referred to in verses 2, 3, 4, 6, 8, 10, 11, 15, 17, and 21.
Anyone who reads scripture for what it actually says will know form the CONTEXT that this is true.
No amount of emotional argumentation will ever change what can be gleaned from a study of the OVERALL texts surrounding these pulled-out-of-context verses WOHP seems to enjoy casting about as nothing more than several disjointed verses ripped out in order to RE-weave together the same old tapestry of falsehood we've all seem for many years. This wasn't a false doctrine he made up himself. He's merely a product of someone else's falsehoods.
BTW