The Holy Spirit is Omniscient.

"These things God has revealed to us through the Spirit. For the Spirit searches everything, even the depths of God. For who knows a person’s thoughts except the spirit of that person, which is in him? So also no one comprehends the thoughts of God except the Spirit of God. Now we have received not the spirit of the world, but the Spirit who is from God, that we might understand the things freely given us by God."- 

1 Corinthians 2:10-12