Reference for Deuteronomy 7:27

The thirteenth principle is that the light sins should be weighty in one's eyes from four angles: The first is that he should not look at the smallness of a sin, but rather at the greatness of the One who commanded it. The second is that the impulse is in control over the light sins, and that may be a cause to do them constantly. And then they will also be considered like weighty ones - when the punishment of all of the times [it is committed] are combined. And they compared it to a silk thread that is loose and weak; but when you combine it many, many times, it becomes a strong rope. And the third is that from his constantly doing the sin, it becomes like something permissible; and he will remove its yoke from upon him. So he will not protect himself against it and he will be considered from those that remove the yoke and are heretics for one thing. And the fourth is that if he defeats the impulse with something small, he will defeat it tomorrow with something big - as our Rabbis, may their memory be blessed, said (Shabbat 105b), "Anyone who breaks vessels in anger should be in your eyes as if he worships idolatry. For this is the way of the evil impulse: Today it says to you thus, on the morrow, it tells you, 'Go worship an idol.'" And it is stated (Genesis 4:7), "Is it not that if you do right, there is uplift, etc." Its explanation [starting with the end of Genesis 4:6] is: "Why has your face fallen? Is it not that if you do right" actions and repent to Me, "there is uplift" - like the usage (in Job 11:15), "Then, free of blemish, you will uplift your head." And it can be understood as an expression of forgiveness. "But if you do not do right, sin couches at the door" (Genesis 4:7): But if you do not repent from that which you sinned, it is not only this iniquity that will lay with you; but rather the impulse crouches at the door to make you sin in all that you do. And it will always defeat you, since it defeated you and trapped you [now] and it also caught you, and you did not repent. "And its urge is toward you," to lead you astray and it ambushes you at every instant. "Yet you can be its master," if you want to overpower it. Therefore you will be punished for the sin, since I gave you the ability to conquer your impulse.

One who walks along in his world without contemplating whether his ways are good or evil is similar to a blind man walking on the bank of a river. His danger is certainly very great and his calamity is more likely than his escape. For negligence in guarding oneself from danger due to natural blindness and negligence due to willful blindness, namely shutting one's eyes by choice and desire is one and the same.