If someone tells you that they know the truth and have another type of book to prove it, it is not judging if you “check it out” using the Word of God as your standard. We should always approach this with love and not a judgmental attitude.
John 13:35 By this shall all men know that ye are my disciples, if ye have love one to another.
Matthew 7:1 Judge not, that ye be not judged.
A very quoted verse, but look at verse five, you will see who the is speaking to.
Matthew 7:5 Thou hypocrite, first cast out the beam out of thine own eye; and then shalt thou see clearly to cast out the mote out of thy brother’s eye. ( Hypocrite, someone acting, an actor, playing a part, pretense) Notice that the verse is not talking to true believers. In fact the Bible tells us we should judge if it is of God.
John 7:24 Judge not according to the appearance, but judge righteous judgment.
1 John 4:1 Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world.
Remember it is not judging, if you are proclaiming God’s word as truth.