Alma clapping his hands upon his brethren was undoubtedly a description of him giving them a blessing before separating (v. 36; see v. 38), as Ammon had done in sending his brethren away to teach the Lamanites (see Alma 17:18). His companions were already members of the church, and therefore, they were not being confirmed or given the gift of the Holy Ghost. They were being blessed by the Lord with the Spirit for their upcoming mission.
The prayer or blessing Alma gave his brethren included instructions that were later given by the Savior in the Sermon on the Mount and to the Nephites in America: to take no thought for the morrow’s food, drink, or clothes (v. 37; see Matthew 6:31; 3 Nephi 13:31). This suggests that these instructions may have been recorded upon the plates of brass at one time, or else Alma may have been inspired by the Spirit to use these same words. After all, Jesus was directing Alma and his brethren at this time just as he was instructing the people in Galilee or in Bountiful. Whichever was the case, Alma’s word was fulfilled (Alma 31:38). His prayer of faith was certainly directed by the Spirit.