Moed Katan 21B

מצוה שאני.

The Talmud answers: A mitzva is different, and since it is a mitzva to put on tefillin, the mourner is required to do so, even during the first 3 days.

תנו רבנן: אבל, שלשה ימים הראשונים אסור במלאכה, ואפילו עני המתפרנס מן הצדקה. מכאן ואילך ⁠— עושה בצינעא בתוך ביתו. והאשה טווה בפלך בתוך ביתה.

§ A baraita states the following baraita: During the first 3 days after his bereavement, a mourner is prohibited from working, even if he is a poor person who is supported by charity. From this point forward, he may do work privately in his own home if he needs to do so. And similarly a woman may spin thread on a spindle in her own home when she is mourning.

תנו רבנן: אבל, שלשה ימים הראשונים אינו הולך לבית האבל, מכאן ואילך הולך, ואינו יושב במקום המנחמין, אלא במקום המתנחמין.

A baraita states in another baraita: A mourner during the first 3 days after his bereavement may not go to another mourner’s house to console him. From this point forward, he may go, but he may not sit among the consolers, but rather in the place of those being consoled, i.e., with the mourners in that house.

תנו רבנן: אבל, שלשה ימים הראשונים אסור בשאילת שלום. משלשה ועד שבעה ⁠— משיב ואינו שואל. מכאן ואילך, שואל ומשיב כדרכו.

§ A baraita states in yet another baraita: A mourner, during the first 3 days after his bereavement, is prohibited from extending greetings to others. From the 3rd day to the 7th day, he may respond when other people address him, but he may not extend greetings to them. From this point forward, he may extend greetings and respond in his usual manner.

שלשה ימים הראשונים אסור בשאילת שלום? והתניא: מעשה ומתו בניו של רבי עקיבא, נכנסו כל ישראל והספידום הספד גדול.

The Talmud asks: Is he really prohibited from extending greetings during the first 3 days of mourning? But isn’t it taught in a baraita: There was an incident and the sons of R' Akiva died, and all the Jews entered to eulogize them with a great eulogy.