Romans 8: 26 - 30
26 Likewise the Spirit helps us in our weakness; for we do not know how to pray as we ought, but the Spirit himself intercedes for us with sighs too deep for words. 27 And he who searches the hearts of men knows what is the mind of the Spirit, because the Spirit intercedes for the saints according to the will of God. 28 We know that in everything God works for good with those who love him, who are called according to his purpose. 29 For those whom he foreknew he also predestined to be conformed to the image of his Son, in order that he might be the first-born among many brethren. 30 And those whom he predestined he also called; and those whom he called he also justified; and those whom he justified he also glorified.
(I wish I could repeat exactly what Father said, but...)
Overall, this reading is saying that the Holy Spirit is so powerful that he is praying for the things that we don't pray or thank God for. Have you ever wondered why something good happened out of something bad and you never stopped to ask God about it? Well, that was the Holy Spirit in work. The spirits "intercedes" for us. Isn't that amazing? It makes me feel good that God loves us so much and has sent us the Holy Spirit. I am so blessed and thankful to be Catholic! :)