Sometimes I like to read the lessons of Daf taught through the Daf Yomi. The Daf Yomi is a system of learning the Talmud which divides it into daily lessons. It takes 7 1/2 years to complete the entire Talmud. I was reading Daf Yomi Avodah Zarah and came across the following lesson.
2) THE PROHIBITIONS OF “V’NISHMARTA” AND “V’LO SASURU”
QUESTION: The Beraisa states that we learn from the verse, “v’Nishmarta mi’Kol Davar Ra” — “You shall guard yourself from any evil thing” (Devarim 23:10), that it is prohibited to have sinful thoughts during the day which might lead to becoming Tamei at night.
There is a similar precept in the Gemara in Berachos (12b). The Gemara there states that the reason why the Chachamim instituted that the Parshah of Tzitzis be recited as part of the reading of Keri’as Shema is because it contains five important topics. One of these topics is that a person must refrain from thinking sinful thoughts about women, which is expressed by the verse, “v’Lo Sasuru [Acharei Levavchem] v’Acharei Einechem” — “You shall not turn away [after your heart and] after your eyes” (Bamidbar 15:39).”
Why are both of these verses — “v’Nishmarta” and “v’Lo Sasuru” — necessary? They both seem to be teaching the same thing!