Parshat Vayera begins with three mysterious men meeting with Avraham. Rashi quotes the Medrash that explains that these men were actually angels. Each of the three angels had a specific task: One was charged with healing Avraham after his circumcision, one was to inform Sarah of her impending pregnancy, and one would go on to destroy
Sodom. The Medrash concludes with a rule: “She’ayn
Malach echad oseh shtei shlichiyot”, one angel is not able to perform two
I believe that this Medrash has particular relevance in an age of multitasking. Though it seems to be the norm to do more than one thing at once, multitasking has been shown to be an inefficient way of accomplishing tasks. We are most efficient when we focus all of our talents and energies into one enterprise, and then move onto something else after the first task is completed. It is usually not in the interest of the person nor of the task to bounce from one activity to the next. Perhaps this is what the Medrash is conveying: If angels are tasked with only one job, then humans should not try to do more. Focus on one thing until completion or until you have done all that you can. And only then move on to something else.
Rashi does quote another source that offers somewhat of a qualifier to this critique on multitasking. The Gemara in Baba Metziah explains that the angel that healed Avraham went on to save