27 The Father, Himself, loves you, because you have loved Me and have believed that I came from God.
At first glance we may think that this is a strange verse, since it appears that the Father’s love for the disciples is a condition of their loving Jesus. It might appear that the implication is the Father only loves the disciples because they love Jesus.
However, we must remember that the source of all love is God, the Father. The best known verse in the Bible tells us that God so loves the world (John 3.16).
In his letter John tells us:
9 In this was the love of God was shown to us, that God has sent His one and only Son into the world that we might live through Him.
10 in this is the love of God, not that we have loved God, but that He loves us and sent His son as the atoning sacrifice for our sins.
11 Loved ones, if God loves us in such a way, we also ought to love one another – 1 John 4.9-11.
The disciples were only able to love Jesus, because the love of God was planted within them. It is the same with us.
His love within them was the reason that they could love Jesus. Their love for Jesus was the evidence that the Father also loved them.
In the case of a man and woman who fall in love, it may be that the man may fall in love with the woman sometime before she falls in love with him. When she does fall in love with him, he continues to love her, but her love for him is not the cause of his love for her.
The second part of this verse has the same kind of implication: that the disciples’ belief in Jesus is the cause of the Father’s love for them.
However, again we must understand that our belief in Jesus is also the gift of God:
 As God’s messenger, I give each of you this warning: Be honest in your estimate of yourselves, measuring your value by how much faith God has given you – Romans 3.12 (NLT). Here we see that faith is the gift of God to us, and we all have a certain measure of it, because God loves us so much.