“While of these emblems we partake … , / Let us remember and be sure / Our hearts and hands are clean and pure.”60 If we participate in the sacrament unworthily, pretending to take upon us the name of Christ and promising to remember him and obey him—and we are not serious about that covenant nor really intending to keep it—we are taking the name of the Lord in vain, and “the Lord will not hold him guiltless that taketh his name in vain” (Exodus 20:7; Mosiah 13:15).
If we know someone is living in sin and is not worthy to partake of the sacrament, we should encourage him not to participate in the sacred ordinance but we should not expel him and reject him; we should work with him, encourage him, minister to him. It may be that he will return, repent, and be healed and saved.
Priesthood leaders—those who preside—are responsible for monitoring the worthiness of participants in sacred ordinances. No one else may forbid someone to take the sacrament.