313. Choosing a Shaliach Tzibbur

Tefillah u’Birkas Kohanim 8:10

We said in 8:9 that one person can fulfill the obligation of prayer on behalf of another only when the other does not know how to daven. An exception to this rule is Rosh Hashana, plus Yom Kippur of the Jubilee year. On those two days, the prayer leader can fulfill the obligation of prayer even for those who know how to daven. This is because the Shemoneh Esrei on these days is extremely long and most people do not know it well enough to be able to have the same intentions as the prayer leader. Therefore, on these days, even one who knows how to daven is given permission to rely on the prayer leader in order to fulfill his obligation (though he need not do so).

Tefillah u’Birkas Kohanim 8:11

Only a person of standing in both wisdom and deeds should be designated prayer leader. An older person is even better. They should try designate someone who has a pleasant voice and is familiar with the texts. One who does not yet have a full beard should not be made prayer leader even if he is a wise person of standing, out of concern for the congregation’s dignity. However, such a person may recite Shema publicly after reaching the age of thirteen and presenting the physical signs of maturity.