Sifrei Devarim 54

¹(Devarim 11:26-27) "blessing and curse": "blessing" — that you hearken; "curse" — that you do not hearken." Similarly (Bereshith 4:7) "If you (Cain) do right, you will bear (a blessing)," and if you do not do right, you will bear (a curse)." R. Eliezer the son of R. Yossi Haglili says: Who "whispers" to you that in "blessing and curse" the Torah meant that the blessing is your hearkening, and the curse, your not hearkening? Compare (Proverbs 18:29) "Death and life are in the power of the tongue; and those who love it will eat its fruit" — The lover of good will eat its fruit and the lover of evil will eat its fruit! R. Eliezer, the son of R. Yossi Haglili says: Who "whispered" it to you? Scripture states (Psalms 24:13-14) "Who is the man who wants life, who loves days to see good? Guard your tongue from evil and your lips from speaking deceit." Similarly, (Proverbs 11:31) "If there is retribution for the righteous one in the land, how much more so for the evildoer and the sinner!" R. Eliezer, the son of R. Yossi Haglili says: Who "whispered" it to you? Scripture states ( Ibid . 16:4) "The L-rd created all for His own sake — even the evildoer for the day of retribution." ³(Devarim, Ibid . 28) "And the curse, if you do not hearken … and you turn away from the way": from the way of life to the way of death. ⁴"that I command you this day, to go after other gods": From here it was derived: If one acknowledges idolatry, it is as if he denies the entire Torah; and if one denies idolatry, it is as if he acknowledges the entire Torah.