1 Thessalonians 2:17 & 18
But, brothers, when we were torn away from you for a short time (in person, not in thought), out of our intense longing we made every effort to see you. For we wanted to come to you - certainly I, Paul, did, again and again - but Satan stopped us.
Paul describes how when they were apart he tried over and over again to get back to see the Thessalonians. He says that it was Satan that prevented it. Some may read this passage and say "how can that be" and "isn't God in control?". Just as in the book of Job, God is in control but He allows Satan to roam the earth for a time and to have some power. It does not diminish God or His power and He uses it for the good of those that love Him.