Mosiah 18

One of the priests of King Noah believed the words of Abinadi and stood for his defense. In response -

"...the king was more wroth, and caused that Alma should be cast out from among them, and sent his servants after him that they might slay him.
4 But he fled from before them and hid himself that they found him not. And he being concealed for many days did write all the words which Abinadi had spoken." (Book of Mormon Mosiah 17:3 - 4)

And Alma -

"...repented of his sins and iniquities, and went about privately among the people, and began to teach the words of Abinadi—
2 Yea, concerning that which was to come, and also concerning the resurrection of the dead, and the redemption of the people, which was to be brought to pass through the power, and sufferings, and death of Christ, and his resurrection and ascension into heaven.
3 And as many as would hear his word he did teach. And he taught them privately, that it might not come to the knowledge of the king. And many did believe his words." (Book of Mormon Mosiah 18:1 - 3)

Alma held meetings with the believers in a secret place called Mormon and -

"...he did teach them, and did preach unto them repentance, and redemption, and faith on the Lord." (Book of Mormon Mosiah 18:7)

And there was at this place of Mormon, "a fountain of pure water". An it is here that we learn important principles on the covenant of baptism for Alma -

"...said unto them: Behold, here are the waters of Mormon...and now, as ye are desirous to come into the fold of God, and to be called his people, and are willing to bear one another's burdens, that they may be light;
9 Yea, and are willing to mourn with those that mourn; yea, and comfort those that stand in need of comfort, and to stand as witnesses of God at all times and in all things, and in all places that ye may be in, even until death, that ye may be redeemed of God, and be numbered with those of the first resurrection, that ye may have eternal life— "(Book of Mormon Mosiah 18:8 - 9)

And for those willing to make that covenant, and -

"...if this be the desire of your hearts, what have you against being baptized in the name of the Lord, as a witness before him that ye have entered into a covenant with him, that ye will serve him and keep his commandments, that he may pour out his Spirit more abundantly upon you?" (Book of Mormon Mosiah 18:10)

And they all were willing to enter into this covenant. And Alma did -

"...baptize every one that went forth to the place of Mormon..." (Book of Mormon Mosiah 18:16)

And they were -

"...filled with the Spirit." (Book of Mormon Mosiah 18:14)

And -

"...filled with the grace of God." (Book of Mormon Mosiah 18:16)

"And they were called the church of God, or the church of Christ, from that time forward. And it came to pass that whosoever was baptized by the power and authority of God was added to his church." (Book of Mormon Mosiah 18:17) The power and authority of God or the Priesthood being a necessary component.

I ask, does baptism and membership in the church alone qualify one to be a child of Christ?

Alma understood the answer to this question for he commanded them after baptism and admission into the Church of Christ for -

"...he commanded them that there should be no contention one with another, but that they should look forward with one eye, having one faith and one baptism, having their hearts knit together in unity and in love one towards another." (Book of Mormon Mosiah 18:21)

In that they should -

"...impart of their substance of their own free will and good desires towards God, and to those priests that stood in need, yea, and to every needy, naked soul...and they did walk uprightly before God, imparting to one another both temporally and spiritually according to their needs and their wants. (Book of Mormon Mosiah 18:28 - 29)

And they were also to -

"...observe the sabbath day, and keep it holy, and also every day they should give thanks to the Lord their God...And there was one day in every week that was set apart that they should gather themselves together to teach the people, and to worship the Lord their God, and also, as often as it was in their power, to assemble themselves together." (Book of Mormon Mosiah 18:23 - 25)

And by doing all these things, Mormon reflects -

"...And thus they became the children of God." (Book of Mormon Mosiah 18:22)