We don't often think of Jesus as a disciplinarian. We like to think of Him as a gentle Shepherd, full of love and mercy. He certainly is that. But He's also a loving shepherd in the sense that He will strike us with the rod, if needed. Here's what He says to the church at Sardis:
Remember, then, what you received and heard. Keep it, and repent. If you will not wake up, I will come like a thief, and you will not know at what hour I will come against you. (Revelation 3:3)
This is after He has told the church that they are dead and that they need to strengthen what remains and is about to die. He calls them to "remember", to think back to what they had been taught by Him through His apostles and their successors. They had received the gospel message and all of its implications. He tells them to "keep it...and repent." They were to hold fast to what they had learned, turn away from whatever was inconsistent with what they learned, and walk in holiness.
Then He tells them that if they will not "wake up" (compare verse 2), He was going to come like a thief. This is an image of coming when someone is not expecting it. He goes on to say, "and you will not know at what hour I will come against you." Notice those last five words: "I will come against you." Those aren't words you might expect Jesus to use toward His church, and yet He does. If they would not repent, He would come against them when they did not expect it.
We also know from other passages, like v. 19, that He does it out of love. But make no mistake, He will come against those who persist in rebellion toward Him.
As is the case with all of these letters, this stands as a warning for us. We need to be careful to not only be externally alive. We need to love God through Christ with all of our heart, soul, mind, and strength, and we need to love our neighbors as ourselves. It's not enough to merely appear to be doing those things. We need to stay awake, lest Christ comes to us like a thief and comes against us.
Again, He would do so in love. But would we rather not avoid discipline? Wouldn't we rather strive to be pleasing to our Savior? Loving parents discipline their children, but they would rather their children obey than receive a spanking. Christ, likewise, is patient toward us, and He would rather us walk in faithfulness than receive rebuke and reproof. May His Spirit help us to be faithful!