The difference between “Le” & “Al” in a b’rachah – Ask the Rabbi
Q. Why do some blessings say le (“to”, e.g. le’hadlik ner shel Shabbat) and others say al (“concerning”, e.g. al n’tillat yadayim)?
A. There are many theories. None works consistently.
Rabbenu Tam says al is used when an action immediately follows the blessing, e.g. al hamilah (“about circumcision”) but le when the action is prolonged, e.g. le’hadlik ner shel Chanukah (“to kindle the Chanukah lights”).
Maimonides says le applies when the action is personal, e.g. le’hitattef batzitzit (“to wrap oneself in a fringed garment”) but al when the action is for others, e.g. al hash’chitah (“concerning animal slaughter”).
These rules sound plausible but they have major exceptions, e.g. le’hadlik ner shel Shabbat and al achilat maror.