Why Does God Allow Temptation?

Luke 4:1-2
[1]Jesus, full of the Holy Spirit, returned from the Jordan and was led around by the Spirit in the wilderness
[2]for forty days, being tempted by the devil. And He ate nothing during those days, and when they had ended, He became hungry.

Jesus was full of the Holy Spirit and yet He was tempted. 
1. Temptation often comes upon a believer with its strongest power when he/she is nearest to God. 
Why does God allow temptation for a believer?.  Look at a tree...storms make roots go deeper and deeper and enable to stand even greater storms.  Oak trees don't become strong within a day or two; they go through different seasons and heavy storms.    
2.  Another example: Fire makes paintings on ceramics permanent and beautiful. Take examples of any missionaries, John Bunyan, William Tyndale or William Carey and many saints, who were going through temptations and testing and became a model for us.
3.  When the devil tries to distract us from following the Lord, we need to overcome by the Word of God.  Then we can feel the touch of our Lord Jesus Christ in the middle of the storms sufferings (Heb. 12:11).  There are many examples from the Bible of people who overcame.
4.  Our Lord Jesus stood the test and came out victorious, defeating the devil.  Jesus said "In the world you have tribulation, but take courage; I have overcome the world." We may experience various tribulations and temptations, but we have a victorious Lord in everything.  Praise the Lord, let's follow His steps.