(1) Be careful to observe only that which I enjoin upon you: neither add to it nor take away from it.

(1) את כל הדבר EVERYTHING [I COMMAND YOU] — light precepts as well as grave ones (Sifrei Devarim 82:1)

(3) לא תסף עליו YOU SHALT NOT ADD THERETO — as, for instance:
* to place five chapters in the Tefillin,

* to employ five species of fruit and plants in the fulfilment of the command of Lulav,

* to recite four instead of three blessings in the Benedictions of the priests (Sifrei Devarim 82:4; cf. Rashi on Deuteronomy 4:2).

(1) לא תספו YOU SHALL NOT ADD — For instance,

* to place five chapters in the Tefillin,

* to employ five species of fruit and plants in the fulfilment of the command of Lulav and * to place five fringes on one’s garment.

Thus, too, must we explain the following words ולא תגרעו, Ye shall not diminish [from it]" (Sifrei Devarim 82:4).

(1) שמע אברהם בקלי ABRAHAM HEARKENED TO MY VOICE when I put him to the test. (2) וישמר משמרתי AND KEPT MY CHARGE — This refers to precautionary measures which are intended to make us avoid the infringement of Biblical prohibitions: such are the Rabbinical inhibition of marriage between relatives in the second degree and the Rabbinical regulations regarding not doing certain acts on the Sabbath (cf. Yevamot 21a).