RICHARD - According to The Purpose of Priesthood Ordinances “Lesson 4: The Purpose of Priesthood Ordinances,” Duties and Blessings of the Priesthood: Basic Manual for Priesthood Holders, Part B, 27, It mentions that the Sacrament is a necessary ordinance for exaltation. I believe this is true with all my heart as part of the sacrament prayer says,"That they may always have his spirit to be with them. Amen. I have a couple of brethren having difficulties grasping this fact that the sacrament is necessary for exaltation. Can you provide me some good scriptural references or Ensigns where our leaders have stated that this is true? Thanks a million.

JOEL - I understand your friends confusion. They are probably thinking of the mandatory saving ordinances that we perform in the temple that are required for salvation for both the living and the dead and don't see how the Sacrament fits in the same category with them. Actually the mandatory ordinances include baptism, confirmation (having the gift of the Holy Ghost bestowed), ordination to the Melchizedek Priesthood (for men), the temple endowment, and eternal marriage. This list probably should not include the Sacrament; if it did we would be performing it in the temple for the dead. Or let's say for example someone is newly baptized into the church, but dies before ever having the opportunity to take the sacrament. Can they still obtain exaltation? I would think so.

I have seen differences of opinion(even among church leaders) as to whether or not the Sacrament should be listed as an ordinance "necessary for exaltation". Perhaps it can be called a saving ordinance if we restrict its application to those of us living members who continue to sin and need the cleansing power that the Sacrament ordinance brings.
In the lesson you refer to we are told, "With sincere repentance it (the sacrament) helps cleanse us of the sins we commit after baptism." A person with unrepented sins cannot enter the Celestial Kingdom (3 Ne. 27: 19); we cannot be saved in our sins (Alma 11: 34, 36-37). Baptism cleanses us of the sins before we join God's kingdom (Acts 22: 16); the Sacrament helps keep us clean of our sins after baptism through repentence and renewing the baptismal covenants (Mosiah 18:8-10, Moroni 4:3). Therefore, we could say that the Sacrament is very important and necessary for the eternal life of those still living on this earth.
Elder Dallin H. Oaks said (read the entire article):

"All ... vital steps pertaining to the remission of sins are performed through the saving ordinance of baptism and the renewing ordinance of the sacrament.
How grateful we are that the Lord has provided a process for each baptized member of His Church to be periodically cleansed from the soil of sin. The sacrament is an essential part of that process.
To have the continuous companionship of the Holy Ghost is the most precious possession we can have in mortality. The gift of the Holy Ghost was conferred upon us by the authority of the Melchizedek Priesthood after our baptism. But to realize the blessings of that gift, we must keep ourselves free from sin. When we commit sin, we become unclean and the Spirit of the Lord withdraws from us."
(Dallin H. Oaks, “The Aaronic Priesthood and the Sacrament,” Ensign, Nov. 1998, 37)

Elder Oaks above calls the Sacrament a "renewing" ordinance, rather than a "saving" ordinance. The Sacrament cleanses us from the soil of sin, allowing the Holy Ghost to be with us. Noone can become perfected and ultimately exalted without this, therefore all faithful latter-day saints desiring exaltation, should participate in this ordinace on a regular basis.

Elder Holland explained the relationship between the ordinances when he said:

"in as many ways as possible we try to take upon us His identity, and we begin by taking upon us His name. That name is formally bestowed by covenant in the saving ordinances of the gospel. These start with baptism and conclude with temple covenants, with many others, such as partaking of the sacrament, laced throughout our lives as additional blessings and reminders." (Jeffrey R. Holland, “Broken Things to Mend,” Ensign, May 2006, 69–71)

Here Elder Holland lists the Sacrament as an "additional blessing and reminder".

Victor L. Ludlow called it an edification-type ordinance but recognized its important relationship to the saving ordinances:

"In addition to the ordinances necessary for salvation and exaltation, many other ordinances and blessings are given through the power of the priesthood to comfort, console, and encourage. Among these edifying ordinances, some provide reminders of our covenant relationship with God and our service relationship with others, especially family members.
Of the edification-type ordinances, the sacrament service comes the closest to being a salvation-type ordinance, both because of its symbolic representation of Christ's atonement and also because it renews the covenant of the baptism and the temple vows."
(Principles and Practices of the Restored Gospel, Victor L. Ludlow )

Regardless of whether or not the Sacrament is a saving ordinance, we need to remember that we cannot be exalted if we do not keep the commandments of God (D&C 14: 7). Partaking of the sacrament is a commandment of God (D&C 59:8–9). After the Nephite disciples partook of the sacrament which Jesus ministered to them, He said:

"Blessed are ye for this thing which ye have done, for this is fulfilling my commandments, and this doth witness unto the Father that ye are willing to do that which I have commanded you." (3 Nephi 18:1-10)

Bottom line is I think the Sacrament ordinance being placed in the "Ordinances Necessary for Exaltation" list in that lesson, is a little confusing to some people who are only thinking of the temple ordinances. The authors probably decided to include it in that list because it goes so well with the others listed; especially baptism.