וכי יהיה איש שנא לרעהו. עַל יְדֵי שִׂנְאָתוֹ הוּא בָא לִידֵי וארב לו, מִכָּאן אָמְרוּ עָבַר אָדָם עַל מִצְוָה קַלָּה, סוֹפוֹ לַעֲבֹר עַל מִצְוָה חֲמוּרָה, לְפִי שֶׁעָבַר עַל לֹא תִשְׂנָא (ויקרא י"ט), סוֹפוֹ לָבֹא לִידֵי שְׁפִיכוּת דָּמִים, לְכָךְ נֶאֱמַר "וְכִי יִהְיֶה אִישׁ שֹׂנֵא לְרֵעֵהוּ וְגוֹ'", שֶׁהָיָה לוֹ לִכְתֹּב וְכִי יָקוּם אִישׁ וְאָרַב לְרֵעֵהוּ וְהִכָּהוּ נָפֶשׁ (ספרי): וכי יהיה איש שנא לרעהו BUT IF A MAN HATE HIS FELLOW [AND LIE IN WAIT FOR HIM] — It is through his hatred that he comes to such a point as to “lie in wait for him”. From here they (the Rabbis) derived their statement: If a man transgresses a light command he will in the end transgress a weighty command; — because he transgressed the command (Leviticus 19:17) “Thou shalt not hate thy brother in thine heart”, he will in the end come to such a point as to shed blood. It is for this reason that it is stated here, apparently redundantly, “but if a man hate his fellow [and lie in wait for him]”, for it ought to have written only: “But if a man rise up and lie in wait for his fellow and smite him mortally” (Sifrei Devarim 186:2).