Jesus had strong words of warning for His disciples about the false teachings being spread by the religious leaders of His day. It would be foolish of us as believers in the modern-day to think that Jesus would not have strong words of warning for many teachers leading the church if He were walking the earth today.
Like leaven, false teaching permeates the body of believers, setting them on a course for sin and failure. False teaching occurs whenever a teacher stops relying on God's Word and starts to add their own thinking and agenda into their teaching. Since the human heart is so easily led astray, it is imperative that those who are charged with teaching the Word of God continuously empty their hearts of self and fill their hearts with the Scriptures, asking the Holy Spirit to guide their teaching into all truth.
The modern church must repent of its false teaching, humble itself before God and ask Him to cleanse it, and bring it back to the righteousness that is only found by following the Scriptures.