Biblical authority is established in two different ways: 1) Direct Command, or Implicit Statement; and, 2) Approved Apostolic Example. All authority comes from these two categories. A Direct Command, or Implicit Statement, is a command that says specifically to do something or not to do something. An Approved Apostolic Example is an example of the early church doing something with the approval of the apostles.
The authority from these two categories takes one of two forms: 1) General, or 2) Specific. General authority gives the what of a command, but leaves it to human judgment the most expedient way (the how) of accomplishing the command. Specific authority defines the how as well as the what of the command.
Expediency can not go beyond the Biblical authority of a Direct Command, or an Approved Apostolic Example; or violate the General or Specific nature of a command. Nothing can be expedient which does not carry out a command of God. It is not an expedient if it makes a General command Specific, or a Specific command General. An expedient can not violate nor create a command; it must allow for compliance with a command.
Apostolic Example is not necessary for something to fall into the category of being a lawful expedient; and neither does the expedient have to be necessary, as long as it neither adds nor subtracts from the command, but allows for compliance with the command.
The same reasoning that is used to justify those things which we accept as lawful expedients must be used to determine the acceptability of any generality or particular before us. It must allow for the carrying out of a command without adding to or subtracting from the command, retaining the General or the Specific nature of the command. There must first be a command before there can be an expedient. This also means respecting the silence of the Scriptures.
However, just as those things we accept as lawful expedients are permissible to use, to demand that they must be used is wrong. For in demanding that they must be used, human opinion is elevated to inspiration, and human doctrine is established the equal of scripture. Conversely, those who have in the past (and continue to do so in the present) opposed expedients as unscriptural elevated their opinion of matters of allowable human judgment to inspiration and their objections to the equal of scripture. Specific authority cannot be made General, nor can General authority be made Specific. Responsibilities and duties cannot be ignored, nor can we enlarge the responsibilities of the church or the Christian according to the scriptures. Therefore, we need to exercise extreme care and caution in determining the acceptability or the unacceptability of anything classified by ourselves or others as an expedient to be sure that we remain constant in our reasoning.
May we ever have before us the command of Jesus to Peter, realizing that the same restrictions apply to us.
And I will give unto thee the keys of the kingdom of heaven: and whatsoever thou shalt bind on earth shall be bound in heaven: and whatsoever thou shalt loose on earth shall be loosed in heaven. (Matthew 16:19 KJV)
Jesus instructed Peter that those things which were to be bound upon men were those things bound in heaven, and that those things which were to be loosed from men were those things which were loosed in heaven. May we never seek to bind more upon men than God has; and, may we never seek to loose men from more than God has.