פירוש על ברכות 34:12

ONE WHOSE DECEASED [RELATIVE] IS LAID OUT [UNBURIED] BEFORE HIM. In Rashi’s text this perek mee shemaso, appears after the perek t’feelas hashachar. However, it appears to R”I, that it should be after היה קורא (as it is in our Gemaros), for at the end of היה קורא the Mishna is discussing rules of k’reeas sh’ma. And here the Mishna also starts with exemptions from k’reeas sh’ma. And in Yerushalmee the text is as we have it.

[HE IS] EXEMPT FROM THE RECITATION OF THE SHEMA. Rashi says that the reason for the exemption is because a person occupied with the plans for burying his relative is similar to a choson who is occupied with involvement in a mitzvoh. Tosfos quotes a Yerushalmee that has a more specific source for this rule.
The Yerushalmee explains the reason for the exemption. Rav Bon said: it is written (D’vorim 16, 3) “so that you should remember etc.” till “all the days of your life”. The verse could have concluded with “all your days” by saying “all the days of your life” it is implying that the obligation to perform mitzvos is for days that you are occupied with life and not on days that you are occupied with death. See the חרדים ספר מבעל פירוש on the Y’rushalmee for an explanation why an additional verse is needed to exempt one when occupied with the death of a relative and the general exemption for one involved in a mitzvoh is insufficient.
This is the text. One whose dead relative is in front of him is exempt from reading sh’ma, and from prayer¹This text is very problematic. We will soon see in the Tosfos on this page that it appears that Tosfos did not have the words and from prayer in his text of the Gemara. and from t’filin.