Alma ends his prayer and at the end performs an action. He “clapped his hands upon all them who were with him.” The simplest explanation of what is happening here is more typically a “laying on” of hands rather than a “clapping:”
“Alma so invoked the power of the Holy Ghost in behalf of his colaborers: “He clapped his hands upon all them who were with him. And behold, as he clapped his hands upon them, they were filled with the Holy Spirit.” The Savior gave authority to the twelve Nephite disciples, by touching them one by one; they were thus commissioned to bestow the Holy Ghost.” (James E. Talmage, Articles of Faith [Salt Lake City: Deseret Book Co., 1981], 150.)
Unquestionably, the result of this action is the conference of the Spirit upon those who were to continue in this missionary journey. Of course we should see this as a special blessing rather than as the conferral of the Gift of the Holy Ghost. This is the blessing of a prophet to his fellow missionaries, a particular invocation of the Spirit for the task ahead.
Linguistic: What is interesting is the “clapping.” This is an unusual usage of the term. We understand the basic action, but clapping is a much more violent action that laying. The discussion that follows is entirely speculative. It is possible that the word clap is a result of some idiosyncrasy of translation. What follows is a discussion of a possible meaning if it really is a direct translation, and that word held a meaning more specific than laying might have.
One of the characteristics of a clap is that the action is accompanied by a noise. One of the little noted aspects of the ancient Mesoamerican psyche is their attention to sounds. These sounds frequently link sounds to deities. The roar of a jaguar was associated with hills and rain (Codex Telleriano Remensis 1:186) and a deity is specifically noted as making loud noises in the mountains (H.B. Nicholson. Topiltzin Quetzalcoatl. University Press of Colorado, 2001, p. 97). We noted a possible connection between the Mesoamerican understanding of the presence of God in thunder and earthquakes when we examined Alma’s experience with the angel in Mosiah 27:11 (see the commentary after that verse).
These elements give us an interesting possibility. If Alma is, as a person of a generally Mesoamerican culture, sensitive to the symbolism of sound as well as action, the noise of the clap may have been a significant signal of the transfer of the Spirit, just as the physical touch would have been. Additionally, we should remember that for both Hebrew and Greek the word that we translate Spirit was more properly breath, or perhaps wind. If Alma had swung a hand hard enough to produce a “clap” it would also have necessarily been accompanied by a rush of wind. Thus we would have a unique set of symbols combining in this particular event, all of which highlight the divine nature of the spirit that is being conferred.