Alma 45:1 - 45:5
Alma 45: 1 Behold, now it came to pass that the people of Nephi were exceedingly rejoiced, because the Lord had again delivered them out of the hands of their enemies; therefore they gave thanks unto the Lord their God; yea, and they did fast much and pray much, and they did worship God with exceedingly great joy.
The Nephites rejoiced over their deliverance from the Lamanites. They gave thanks to their God because they knew it was He who gave them to power to drive them from their lands. They gave their thanks through prayer and fasting.
To give thanks through fasting has always been an usual concept to me. I think that having a feast or dinner is how most people think of how to celebrate, but here it is just the opposite. We show our thanks by fasting for a period of time.
Alma 45: 2 And it came to pass in the nineteenth year of the reign of the judges over the people of Nephi, that Alma came unto his son Helaman and said unto him: Believest thou the words which I spake unto thee concerning those records which have been kept?
In the 19th year of the reign of the judges, Alma had a priesthood interview with his son Helaman. Alma asked him if he knew of the importance of keeping up of the records that had been kept since the descendants of Lehi had come to the land of promise.
Alma 45: 3 And Helaman said unto him: Yea, I believe.
Helaman affirmed to his father that he knew of the importance of keeping up the records.
Alma 45: 4 And Alma said again: Believest thou in Jesus Christ, who shall come?
Alma asked if he also had a testimony of Christ and that he would come sometime to the earth as a mortal.
Alma 45: 5 And he said: Yea, I believe all the words which thou hast spoken.
Helaman again said he believed all his father had said about the coming of the Messiah.