John 14.1 cont.
1 “Do not allow your heart to be agitated; you believe in God (or ‘believe in God’), also believe in Me.
The second phrase of this sentence can easily be translated in two ways.
1 It may be a statement Jesus made about the current state of His disciples faith, declaring that they did believe in God. Therefore, He would have been affirming their belief, and establishing it in their hearts.
We all appreciate these kinds of words, because when they are spoken about us we know that others can see where our faith is.
Paul wrote to the Colossians and commended them:
 We always thank God, the Father of our Lord Jesus Christ, when we pray for you,  because we have heard of your faith in Christ Jesus and of the love you have for all the saints – Colossians 1.3-4.
Such words of commendation are given to bring us encouragement in what we are doing.
Jesus may have been doing this to the disciples. Jesus knew the trials that He would be going through, and what this would mean for them. In a similar manner, through the Holy Spirit, Jesus may speak to us to bolster our faith, preparing us for the work He has called us to do.
2 This phrase is just as capable of being translated as a command from Jesus.
In which case, Jesus is encouraging His disciples to place their faith, their trust, and their confidence in God and in Himself. There had been times when Jesus had spoken to them about their small amount of faith. One such time was when the disciples had forgotten to take some bread with them. This was after Jesus had fed the five thousand and also the four thousand. Jesus knew what they were thinking, so He said, “You have so little faith! Why are you worried about having no food? – Matthew 16.8.
Now was the time to command His disciples to be firm in their faith in God and in Himself.
Jesus knows the times when our faith is likely to falter. We can be thankful that He does not leave us in that state, but, again through the Holy Spirit, comes along side us to gently command us to be steadfast in our faith in God and in Him.