The pasuk of vedibarta bam

Gemara: teaches that a person’s
primary speech should be Torah.

Yerushalmi- teaches that certain
obligations can only be fulfilled by the person himself. It isn’t sufficient to
just listen to another person and discharge his obligation via shomea ke’oneh. E.g. krias shema.

Gemara Megila- one needs ten people in order to fulfill the
halacha of shomea ke’oneh  with regards to krias

Magen Avraham-. Three conditions for krias shema: a]
listening  b] responding amen   c] in the presence of ten people.

Why the extra condition for krias shema?

There are two types of shomea ke’oneh:

  1. listening to another
    person’s recitation to discharge his own obligation
  2. where the one listening is
    considered as if he himself actually articulated the bracha.

Possible answer:  The Magen
Avraham is of the opinion that one is required to articulate himself the krias shema, and relying on someone else’s recitation
would necessitate, in addition to listening, the extra step of ten people and
responding amen.

We find the same concept by the obligation to recite 100 brochos on shabos.

The Rosh: listen to others and respond amen to accumulate 100

Ma’adanei Yom Tov asks: Why necessary to add the amen? Isn’t
shomea ke’oneh sufficient?

Answer-to be considered as if he articulated the bracha himself, one needs the added benefit of
responding amen.