Like I said before, the Bible is not the sum of all of God's revelations.. However, if you have read the verses I've posted previously, ie
Matthew 16:18-19
18 And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it.
19 And I will give unto thee the keys of the kingdom of heaven: and whatsoever thou shalt
bind on earth shall be bound in heaven: and whatsoever thou shalt loose on earth shall be loosed in heaven.
Matthew 18:18
18 Verily I say unto you, Whatsoever ye shall bind on earth shall be bound in heaven: and whatsoever ye shall loose on earth shall be loosed in heaven.
Tells us that WHATSOEVER Peter was to bind on earth would be bound in heaven. This includes marriage. Joseph Smith was give this same power and authority and was able to seal marriages while on this earth for time and all eternity. This power and authority continues with all the living heads of the church and is had by Russell M. Nelson today.