Seeming Contradictions

What is the distinction between these two scripture passages? How are they rightly divided to find the truth?

Mark 9:38 And John answered him, saying, Master, we saw one casting out devils in thy name, and he followeth not us: and we forbad him, because he followeth not us.
Mark 9:39 But Jesus said, Forbid him not: for there is no man which shall do a miracle in my name, that can lightly speak evil of me.
Mark 9:40 For he that is not against us is on our part.
Mark 9:41 For whosoever shall give you a cup of water to drink in my name, because ye belong to Christ, verily I say unto you, he shall not lose his reward.

Mat 7:21 Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.
Mat 7:22 Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works?
Mat 7:23 And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.

Sometimes we see passages of scripture that seem to to be saying the same things but with opposite conclusions. It is good to seek the LORD about these and sleep on it. In the morning I usually have insights about what are the differences.Let me begin with this last verse. The time is judgment day when the thoughts and intents of the heart are made known. First off, are these people saved by faith in Jesus Christ? Apparently they were not even connected to Jesus by faith for he said "I never knew you". They may have had miracle revival meetings, drawing huge crowds and made lots of money. They may have been well know, a big name in ministry. They may have been using Jesus name and by the faith of the one in need, God had mercy on them even healing them. The false teachers may have read the gospel message and it may have been followed by signs and wonders, but they never were born again, it was all hypocrisy and their hearts were not seeking to please God, but to glorify themselves. They made disciples unto themselves, perhaps being a leader of a very large church.The end result was "depart from me, ye that work iniquity." Why did this happen and in the verses from Mark 9, Jesus was seemingly saying something opposite?

In Mark 9, Jesus said leave them alone, for who is not against us is for us. Can anyone cast out demons in Jesus' name if we are not in Jesus?

Act 19:13 Then certain of the vagabond Jews, exorcists, took upon them to call over them which had evil spirits the name of the Lord Jesus, saying, We adjure you by Jesus whom Paul preacheth.
Act 19:14 And there were seven sons of one Sceva, a Jew, and chief of the priests, which did so.
Act 19:15 And the evil spirit answered and said, Jesus I know, and Paul I know; but who are ye?
Act 19:16 And the man in whom the evil spirit was leaped on them, and overcame them, and prevailed against them, so that they fled out of that house naked and wounded.
Act 19:17 And this was known to all the Jews and Greeks also dwelling at Ephesus; and fear fell on them all, and the name of the Lord Jesus was magnified.
Act 19:18 And many that believed came, and confessed, and shewed their deeds.
Act 19:19 Many of them also which used curious arts brought their books together, and burned them before all men: and they counted the price of them, and found it fifty thousand pieces of silver.
Act 19:20 So mightily grew the word of God and prevailed.

The difference I see in the two Bible passages is that the disciples were doing the judging before judgment day in Mark 9 and Jesus was doing the judging at judgment day in Matthew 7. In the parable of the wheat and the tares, it spoke of the kingdom of God being of wheat, the saved and of tares or weeds that resemble the wheat. They are to be left alone until the final day, and then the angels would sort the good from the evil. Jesus will exam every heart and life.

How many times have we served God half heartedly? How often have we done things for God with the wrong motives? How often have we done things in the flesh, not seeking God? What if Jesus had come then and we were examined? Many may be serving God with the wrong motives.

Php 1:14 And many of the brethren in the Lord, waxing confident by my bonds, are much more bold to speak the word without fear.
Php 1:15 Some indeed preach Christ even of envy and strife; and some also of good will:
Php 1:16 The one preach Christ of contention, not sincerely, supposing to add affliction to my bonds: Php 1:17 But the other of love, knowing that I am set for the defence of the gospel.
Php 1:18 What then? notwithstanding, every way, whether in pretence, or in truth, Christ is preached; and I therein do rejoice, yea, and will rejoice.

What if satan were to send false teachers and prophets? These would appear as servants of God , but with false motives.

2Co 11:13 For such are false apostles, deceitful workers, transforming themselves into the apostles of Christ.
2Co 11:14 And no marvel; for Satan himself is transformed into an angel of light.
2Co 11:15 Therefore it is no great thing if his ministers also be transformed as the ministers of righteousness; whose end shall be according to their works.

It is in the final judgment that every work will be revealed for it's worth. False ones will not get by Jesus.

1Co 3:8 Now he that planteth and he that watereth are one: and every man shall receive his own reward according to his own labour.
1Co 3:9 For we are labourers together with God: ye are God's husbandry, ye are God's building.
1Co 3:10 According to the grace of God which is given unto me, as a wise masterbuilder, I have laid the foundation, and another buildeth thereon. But let every man take heed how he buildeth thereupon.
1Co 3:11 For other foundation can no man lay than that is laid, which is Jesus Christ.
1Co 3:12 Now if any man build upon this foundation gold, silver, precious stones, wood, hay, stubble;
1Co 3:13 Every man's work shall be made manifest: for the day shall declare it, because it shall be revealed by fire; and the fire shall try every man's work of what sort it is.
1Co 3:14 If any man's work abide which he hath built thereupon, he shall receive a reward.
1Co 3:15 If any man's work shall be burned, he shall suffer loss: but he himself shall be saved; yet so as by fire.
1Co 3:16 Know ye not that ye are the temple of God, and that the Spirit of God dwelleth in you?
1Co 3:17 If any man defile the temple of God, him shall God destroy; for the temple of God is holy, which temple ye are.

From this study I see that I must be careful about how I serve God and what is in my heart. We are to be connected to Jesus through faith and being born again of his spirit, children of God for his service. It is not our job to condemn anyone's ministry. We are disciples who know and do the will of God through knowing his scriptures. We are not to judge people before the time. But we are to be careful to keep evil from taking over; not letting false ones speak to the sheep we care for. Jesus is the final judge and we are not to judge other before the time, lest we be judged. But we are to check their spirit and be careful. In one verse Jesus said leave them alone if they cast out demons they are for us. In the last verse he was condemning people for saying they cast out demons, because they did not have a relationship with him, they were unsaved and maybe were liars. We stumble around in the dark until we are saved. God had patience and so must we have patience. Jesus will judge, so we must be in him if our work is to remain. All we do is by His Spirit.