48 Be ye therefore perfect, even as your Father which is in heaven is perfect.(Matt 5:48)
1 ¶ I therefore, the prisoner of the Lord, beseech you that ye walk worthy of the vocation wherewith ye are called,(Eph 4:1)
4 Thou hast a few names even in Sardis which have not defiled their garments; and they shall walk with me in white: for they are worthy.(Rev 3:4)
Anti-Mormons will often describe the Gospel as declared by the LDS faith as being an "Impossible Gospel of Mormonism". They assert that Mormons must be essentially sinless to be worthy of salvation in the celestial kingdom. They make this assertion based on a highly selective and flawed reading of works by LDS authors such as Spencer W. Kimball's "The Miracle of Forgiveness", without any attempt to provide context or, for that matter, complete citations from within the work, or in the larger scheme, from official sources.
So let's break this down for a moment. The "perfect" spoken of in Matthew 5:48 is not about an inerrant, sinless type of existence. The word translated as "perfect" is better rendered "complete". Be complete as the Father is complete. This statement comes at the end of the Beatitudes, the nature of existence about which we should strive to be. None of the Beatitudes say "Don't ever sin", since such an admonition is patently impossible for a human. Instead, it encourages us to love, be kind, be forgiving and make peace with all people. The closest Jesus comes to saying "be sinless" is in noting the "pure in heart" shall see God (which, to state the obvious, means Jesus is not asserting he is God, or else it would have been fulfilled for those who are also NOT pure in heart). The word pure, "Katharos" (Gk) (like the word "cathartic"), means to be clean, innocent, unstained with the guilt of anything, having pure desires.
The state of "purity" is attained only through the Atonement of Christ through faith. One cannot be "pure in heart" if they have no desire to be pure in the Biblical sense, or they will not seek purity through Jesus.
We know this to be the case because Paul tell us to be pure, and even more significantly, John notes there are in fact "worthy" people in Sardis, who shall walk in white (symbol of purity) with Jesus. These are part of the series of comments about the various Churches, and at the end John notes that Jesus will make those that over come pillars in the Temple of God, never to go out again, with God's name written on their forehead. (Rev 3:12, 18-21).
Revelation 3 makes it clear that Jesus is the source of purity (Rev 3:18), but that we are in fact responsible for accepting him, retaining him and repenting as we make errors, which is how we are worthy (Rev 3:20; 3:10 and 3:19, respectively).
How are we worthy then? Not by unfailing exactness or never failing obedience, but by becoming complete. That means that when we are disobedient, we repent, but we try to stay clean. If perfection were the requirement for the LDS, as ascribed by its critics, then the LDS Church would have excised those "corrupt" passages of scripture which offer us, indeed command us, to repent. We would also have no need for talking the sacrament weekly, or "repent speedily"(D&C 65:13), one of some 75 direct admonitions in the D&C for people, in and out of the Church, to repent.
So be worthy. That means have the attitude of pure thoughts, eschew evil, and repent of your sins through the atonement of Jesus Christ, and therefore walk worthy of the high calling of salvation, walking in white with Jesus. How great is that opportunity given to mankind. How sad for those who think accepting Christ is only done with the mouth or heart, and not the feet (Romans 10:8-16) or by obedience.
Be perfect this Christmas.