This parasha ends with the lines chosen for the third verse of the Shema. A key reason for the tzitzit is given “that you see it and remember all the G-d’s commandments and perform them; and not explore after your heart and after your eyes after which you stray.”
R Eli Munk referred to the Talmud (Berachot) that “after your heart” refers to the sin of heresy, “after your eyes” refers to the sin of debauchery, and “after which you stray” refers to the contemplation of idolatry. He wrote that the contemplation of sin may be worse than the act because the act is time limited whereas the contemplation may be unlimited, and that tzitzit can be a continuing reminder.
Yeshayahu Leibowitz wrote that the eyes are “spiritual eyes,which understand and recognise things”, the heart is our drives.He argued that the logic of the Torah was contrary to the view that it is simply an ethical document, a study text for the moral perfection of man.
Leibowitz pointed to the next sentence in the Shema, the immediate reason being “I am your G-d”. Leibowitz argued that all ethical decisions stem from the fact that man regards himself as standing before his fellow man, whereas religious faith is based on the fact that man sees himself as standing before G-d.
Leibowitz argued that the intentions behind the act could be ethical, or faith based and that this consideration could change the way the act was judged. Ethical priorities might change over time but faith based commandments have remained more constant.