Rav Chisda explains that if one speaks between placing the tefillin shel yad and the tefillin shel rosh, an additional blessing must be recited upon the shel rosh. From this, one can infer that if no interruption occurs, only one blessing is required. However, this poses a difficulty in light of Rabbi Yochanan's statement that there are separate blessings for the shel yad and shel rosh. Abaye and Rava resolve this conflict, yet their resolution is interpreted differently by Rashi and Rabbeinu Tam, resulting in two distinct customs.

The tefillin shel yad is placed first, followed by the shel rosh. When removing them, the order is reversed: the shel rosh is removed first, then the shel yad. This specific sequence is derived from the verse in Devarim 6:8.

If one dons tefillin early in the morning before the proper time has arrived, the blessing is recited the moment the obligation begins. As stated in Berakhot 9b, this occurs when it becomes light enough to recognize an acquaintance from a distance of four cubits.

There are three opinions regarding how late one may wear tefillin: until sunset, until the last people leave the market, or until one goes to sleep. Two versions of Rav Nachman's ruling exist - either supporting or opposing the middle position. This ruling either aligns with or contradicts the practice of Rav Chisda and Raba bar Rav Huna, who would pray Maariv while still wearing tefillin.

A challenge is raised against Raba bar Rav Huna's practice based on his own statement implying that tefillin must be removed as darkness falls. This is resolved by explaining that his statement referred specifically to Shabbat. There are two different derivations for the exemption of tefillin on Shabbat: one links it to the exemption of wearing tefillin at night, while the other does not.

Is it forbidden to don tefillin at night? If so, does one transgress a positive commandment or a negative one?

One should touch the tefillin while wearing them to maintain constant awareness of them. This is derived via a kal v'chomer (a fortiori argument) from the tzitz (the Kohen Gadol's forehead plate).

Tefillin are worn on the left hand, as derived from various verses indicating that the word "yad" refers specifically to the left hand.