So there’s this group of people called Jehovah’s Witnesses that use Christian language to describe a religion that denies key parts of the Christian worldview. Since you may might them knocking on your door to tell you about their worldview, it might be worth it to read this post from J. Warner Wallace over in advance.
I’ll just post a snip of the first I use when they come to my door. It’s also the first on Wallace’s list:
If I am to accept the teaching of the Jehovah’s Witness religion, I am first going to have to trust the source of this teaching. But how can I trust someone who claims to speak for God when they have been wrong about prior predictions?
There are a number of false predictions made either by Charles Russell, subsequent leaders of the church or the Watchtower Organization itself, including this limited sampling:
1886 The Millennial Reign Has Already Begun “The outward evidences are that the marshalling of the hosts for the battle of the great day of God almighty, is in progress while the skirmishing is commencing.” (Watchtower reprints 1, page 817 January 1886)
1897 The Millennial Reign Began in 1874 “ Our Lord, the appointed King, is now present, since October 1874” (Studies in the Scriptures, Vol. 4, page 621)
1899 The Times Described in Revelation 16 Have Begun “…the ‘battle of the great day of God Almighty’ (Revelation 16:14), which will end in A.D. 1914 with the complete overthrow of earth’s present rulership, is already commenced.” (The Time Is at Hand, page 101 – 1908 edition)
1916 The Millennial Reign Began in 1873 “The Bible chronology herein presented shows that the six great 1000 year days beginning with Adam are ended, and that the great 7th Day, the 1000 years of Christ’s Reign, began in 1873.” (The Time Is at Hand, page ii)
1917 Armageddon Has Begun “The present great war in Europe is the beginning of the Armageddon of the scriptures.” (Pastor Russell’s Sermons, 1917, page 676)
1918 The Saints Will Be Resurrected in 1925 “Therefore we may confidently expect that 1925 will mark the return of Abraham, Isaac, Jacob and the faithful prophets of old, particularly those named by the Apostle in Hebrews 11, to the condition of human perfection.” (Millions Now Living Will Never Die, page 89)
“1925 shall mark the resurrection of the faithful worthies…We are standing at the very portals of that blessed time!” (Millions Now Living Will Never Die, page 105)
1922 Jesus Will Return in 1925 “The date 1925 is even more distinctly indicated by the Scriptures than 1914.” (The Watchtower, September 1st, 1922, page 262)
1923 Jesus Will Return in 1925 “Our thought is that 1925 is definitely settled by the Scriptures. As to Noah, the Christian now has much more upon which to base his faith than Noah had upon which to base his faith in a coming deluge.” (The Watchtower, April 1st, 1923, page 106)
1925 Jesus May Return in 1925 “The year 1925 is here. With great expectation Christians have looked forward to this year. Many have confidently expected that all members of the body of Christ will be changed to heavenly glory during this year. This may be accomplished. It may not be. In his own due time God will accomplish his purposes concerning his people. Christians should not be so deeply concerned about what may transpire this year.” (The Watchtower, January 1st, 1925, page 3)
1940 Armageddon is Eminent Within the Year “The year 1940 is certain to be the most important year yet, because Armageddon is very near.” (Informant, May 1940)
1941 Jesus Will Return in Months “Receiving the gift, the marching children clasped it to them, not a toy or plaything for idle pleasure, but the Lord’s provided instrument for most effective work in the remaining months before Armageddon.” (The Watchtower, September 15th, 1941, page 288)
1946 Armageddon is “At the Door” “…the disaster of Armageddon, greater than that which befell Sodom and Gomorrah, is at the door.” (Let God be True, 1946, page 194)
1968 Jesus Will Return in 1975 “Why are you looking forward to 1975?” (The Watchtower, August 15th, 1968, page 494)
“Just think , brothers, there is only 90 months left before 6000 years of mans existence on earth is completed… the majority of people living today will probably be alive when Armageddon breaks out.” (Kingdom Mystery, March 1968, page 4)
This is the quickest way to see why you should not convert to their organization. In the Bible, it’s a serious crime to make a prediction about the future and then have it not come true. It’s actually a capital offense, and it’s something that “false prophets” do. But it happens all the time with JWs. Just remind them of this and say “I cannot be affiliated with any organization that fails to get their truth claims right over and over again, because it shows me clearly that they don’t speak for God”.
Wallace actually has the quote from the Bible in his point 3:
20 But the prophet who speaks a word presumptuously in My name which I have not commanded him to speak, or which he speaks in the name of other gods, that prophet shall die.’
21 You may say in your heart, ‘How will we know the word which the Lord has not spoken?’
22 When a prophet speaks in the name of the Lord, if the thing does not come about or come true, that is the thing which the Lord has not spoken. The prophet has spoken it presumptuously; you shall not be afraid of him.
The other one I use is John 1:1, which Wallace’s first point under the “Biblical Questions” heading.
If you want a longer treatment of this topic, check out Michael Licona’s PDF document on Mormonism and Jehovah’s Witnesses.