Rav Asi said: as long as the obligation to bury him rests upon a person, it is regarded as if [the dead] lies before him, as it is said, "that I may bury my dead from before me" (Genesis 23:4). But was she lying before him at that moment? Is it not written, "And Abraham rose up from before his dead"? Rather, as long as the obligation to bury him rests upon a person, it is regarded as if the dead lies before him. And one who watches over the dead, even though it is not his own dead, [is exempt from the commandments]; even though he is not watching over it, he does not recite the blessing. And if he wishes to be stringent upon himself, he is not permitted.
While the Duty to Bury Remains the Dead Lies Before You
Yalkut Shimoni on Torah 102:15
רַב אָסִי אָמַר, כָּל זְמַן שֶׁמֻּטַּל עָלָיו לְקָבְרוֹ כְּמוּטָל לְפָנָיו דָמִי, שֶׁנֶּאֱמַר וְאֶקְבְּרָה מֵתִי מִלְּפָנַי, אָטוּ הַהִיא שַׁעְתָא קַמֵּיה הֲוָה רַמְיָא, וְהָכְתִיב וַיָּקָם אַבְרָהָם מֵעַל פְּנֵי מֵתוֹ, אֶלָּא כָּל זְמַן שֶׁמֻּטַּל עָלָיו לְקָבְרוֹ כְּמוּטָל לְפָנָיו דָּמִי, וְהַמְּשַׁמֵּר אֶת הַמֵּת אַף עַל פִּי שֶׁאֵינוֹ מֵתוֹ מֵתוֹ, אַף עַל פִּי שֶׁאֵינוֹ מְשַׁמְּרוֹ, אֵינוֹ מְבָרֵךְ וְאִם רָצָה לְהַחְמִיר עַל עַצְמוֹ אֵינוֹ רַשַּׁאי.