HOLY SPIRIT
"The Spirit is God's guarantee that he will give us the inheritance he promised and that he has purchased us to be his own people. He did this so we would praise and glorify him."
When we receive God's spirit, we will speak with tongues. That's a language that we haven't learned before. This is how we know that God is in us: He speaks the words of praise and prayer that we need to say. A lot of the time, we don't know how to pray, but He knows what we should say. We need Him in our hearts.