On the other hand, there are noted poskim (Chidushei HaRim, Avnei Nezer and Birkei Yosef, among others) who disagree with this position. They rule that a minor – even if he counted with a berachah for purposes of chinuch – does not count with a blessing once he attains maturity in the middle of sefirah because his prior counting is considered different from his present counting as an adult, which is biblical mandated.
Still another school of opinion is represented in the responsa of the Chesed LeAvraham (56), Maharash Engel (7:112), and Tzitz Eliezer (14:20), who all rule that even if the young man had not counted the omer while a minor, he may start to count with a blessing upon reaching maturity. They reason that the obligation to count applies from the day the boy reaches the age of bar mitzvah, and therefore the concept of “sheva Shabbatot temimot” also starts for him on that day.
The Piskei Teshuvot nevertheless concludes that we follow the first (lenient) rule mentioned above – that a minor who has attained the age of bar mitzvah during Sefirat HaOmer may continue counting with a berachah if he has not missed a single day of counting while still a minor. He adds that such a young man should not be put in a position to serve as a representative to fulfill another adult’s obligation “by counting the omer before the congregation.” In his view, counting the omer is a biblical obligation for an adult, whereas the obligation of a recent bar mitzvah boy might only be rabbinic according to some poskim.
The discussion presented by Rabbi Rabinowitz is also found in Minchat Chinuch (mitzvah 306). The author discusses the arguments of both sides and concludes that since the bar mitzvah boy had already started counting the omer – albeit as someone not actually required to do so – he may complete the count; his counting as a minor is not discounted.
In his Teshuvot VeHanhagot (Orach Chayim 147), Rav Moshe Shternbuch explains that we follow this opinion since we view the obligation of counting the omer today as rabbinic (see Menachot 66a and Rashi ad loc., that it is only zecher le’mikdash – a remembrance of the time of the Temple).
(To be continued)