D&C 20

Moroni wrote that in his day -

"...they were not baptized save they brought forth fruit meet that they were worthy of it.
2 Neither did they receive any unto baptism save they came forth with a broken heart and a contrite spirit, and witnessed unto the church that they truly repented of all their sins.
3 And none were received unto baptism save they took upon them the name of Christ, having a determination to serve him to the end." (Book of Mormon Moroni 6:1 - 3)

An essential requirement to be considered for baptism is a witness to the Church that one has truly repented of their sins. I don't believe this is just verbal witness, but also an active witness or manifestation of willingness, obedience, participation, and works. In modern day, the Lord has given much the same instruction -

"....All those who humble themselves before God, and desire to be baptized, and come forth with broken hearts and contrite spirits, and witness before the church that they have truly repented of all their sins, and are willing to take upon them the name of Jesus Christ, having a determination to serve him to the end, and truly manifest by their works that they have received of the Spirit of Christ unto the remission of their sins, shall be received by baptism into his church." (Doctrine and Covenants Section 20:37)

These same principles apply after baptism in in instruction and partaking of the sacrament -

"The elders or priests are to have a sufficient time to expound all things concerning the church of Christ to their understanding, previous to their partaking of the sacrament and being confirmed by the laying on of the hands of the elders, so that all things may be done in order.
69 And the members shall manifest before the church, and also before the elders, by a godly walk and conversation, that they are worthy of it, that there may be works and faith agreeable to the holy scriptures—walking in holiness before the Lord." (Doctrine and Covenants Section 20:68 - 69)

Some members feel that baptism and partaking of the sacrament is just a personal thing between God and man, but that isn't the mind and will of the Lord. Candidates for baptism and members of the Church have an obligation before priesthood leaders to, I repeat again -

"...manifest before the church, and also before the elders, by a godly walk and conversation, that they are worthy of it, that there may be works and faith agreeable to the holy scriptures—walking in holiness before the Lord." (Doctrine and Covenants Section 20:69)

There must always be an outward representation of an inward commitment to keep the covenants we make at baptism.