Why is a man's Simchah in his mouth's answer?
Rashi: Via a soft answer and speaking pleasantly, people love him.
Rashi citing Eruvin 54a #1: One who learns texts [of teachings] has Simchah when Ma'aneh b'Fiv (he can answer questions). Then, his learning lasts and he rejoices in it.
Eruvin 54a #2: A man has Simchah when "Davar b'Ito Mah Tov" (he can answer timely questions, e.g. laws of Pesach during Pesach.)
R. Yonah: One rejoices in his answer when he is able to answer correctly.
Malbim: If the laws of Chachmah are arranged on his lips, to the point that when they ask him something, he can answer immediately, he has Simchah from this. The mouth hints to Chachmah.
What do we learn from "Davar b'Ito Mah Tov"?
Rashi: Refer to 15:23:1:3.
R. Yonah: One should overcome his nature - he desires to say everything that crosses his heart. He must rule over this, and speak only what is proper in its time, even though a man has Simchah via answering.
Malbim: If one answers a matter when it is needed, this is good. His Chachmah helps when it is needed; this is the ultimate good. This is better than "Ma'aneh Fiv", which is Simchah only for him; here he benefits also others when needed.
