Whether a person is being led of the Spirit of God is determined of God only, so we must seek God to lead us in spite of our own will and way, which may deceive us and we will not know it. Was Isaiah led of God to walk naked and barefoot? Apart from what God says about Isaiah in those passages in Isaiah, can anyone make a case for determining the mind of God about whether anyone ought to be doing something like that? After Peter went through his humbling experience, the Lord told him that he was in the habit of determining for himself what he should be doing, but when he was converted he would understand how to allow the Lord to lead him where he would not normally go.
Isaiah was a prophet but you are not. Peter was an apostle/prophet but you are not! God spoke directly to prophets but that is not how he speaks today (Heb. 1:1). There are valid tests to try prophets and ignorning those tests is not only disobedience to God's word but foolish. You are confusing apples with oranges.
Did the disciples follow this plan in picking Matthias?
Yes, they did! Peter referred to what the Scriptures said and then followed it by prayer - God's Word and prayer.
Acts 1:16 Men and brethren,
this scripture must needs have been fulfilled, which the Holy Ghost by the mouth of David spake before concerning Judas, which was guide to them that took Jesus.
17 For he was numbered with us, and had obtained part of this ministry.
Acts 1:20 For
it is written in the book of Psalms, Let his habitation be desolate, and let no man dwell therein: and his bishoprick let another take.
What about Paul's plan to spend time at Corinth (1 Cor. 16:7), was this obvious by examining the evidences in scripture and among the brethren and elders? Paul would have gone to Asia to preach the gospel there, but was forbidden of the Holy Ghost (Acts 16:6). Our actions may be conformed to the word of God, but we still must have the God of the word leading us in our steps. ("The steps of a righteous man are ordered of the Lord").
Paul was a prophet and apostle you are not! God spoke directly to Paul as God spoke to his prophets. You quote a portion of Psalms but have you read Psalm 119 which is the longest chapter and the Bible???
I was once involved in a charismatic church when I was much younger, and I am a little put off by some of those things passing as "testing the spirits." I stay away from any application of this verse apart from holding those speaking the word of God to the letter of the word of God. In other words, if they are venturing into error, we should expose that error by unfolding the word of God in the face of that error.
You are doing exactly what the Charismatics do! They don't test the Spirits by the objective word of God but by their subjective feelings! Have you read the design for God giving His word in 2 Timoth 3:16-17???
The issue may get a little complicated when we venture into the realm of differences between the written word (letter of the law) and the Spiritual leading of God (according to the Spirit of the word). Was Isaiah violating the word of God by walking around naked?
Again, Isaiah was a prophet and God spoke directly to His prophets but you are not a prophet.
Did David sin by eating the shewbread?
David did not sin because his actions were in harmony with the intent of that law. The bread was a symbol of Christ as the bread of LIFE and the life of his men were at risk.
Were the disciples in sin for harvesting corn on the sabbath?
The Sabbath law never condemned every kind of work but work of only one sort (Isa. 58:13). Jesus said "It is LAWFUL to DO GOOD on the Sabbath."
Every item on your list so far is simply misapplication of scripture because of misintepretation of scritpure.
The fact is, as I see it, we cannot know the will of God without asking Him, and we cannot do the will of God without Him working His own will through us.
The reason you cannot see is because you are blind! What do you think the Word of God is? It is his REVEALED WILL! To say that one cannot know the will of God is to proclaim their own utter ignorance of God's Word and why it is given.
Jesus said, Sanctify them by thy truth, THY WORD IS TRUTH! The Word is the Sword of the Spirit and the Spirit NEVER contradicts His own Word as He is the author. If there is a contradiction it is in the head of the reader who fails to intepret the scriptures by context.