Sahl ibn Sa`d narrated that the Messenger of Allah (peace be upon him) said:
"Beware of minor sins because the example of minor sins is like a group of people who camped in a valley. Then a person brought a stick and another brought a stick until they gathered a pile to cook their food. Likewise minor sins [their doers gather them one by one and], when their doers commit them, they destroy them." (1)
Explanation of the Hadith:
The meaning of minor sins is the sins which their doers believe they will not harm. The meaning of the Hadith is exhortation not to underestimate sins, and holding oneself accountable for them because neglecting them will lead to destruction because minor sins may turn to be major as Ibn Battal said.(2)
Lessons gained from the Hadith:
1- Sins are divided into major and minor sins as Allah (may He be Exalted) said: "If you avoid the great sins which you are forbidden to do, We shall expiate from you your (small) sins." [Surat An-Nisa': 31]. Allah also says: "Those who avoid great sins (See Verses: 6:152, 153) and Al-Fawâhish (great sins and illegal sex) except the small faults."
[Surat An-Najm: 32]. The most correct views in the definition of major sins is: It is the sin which there is a prescribed punishment for its doer or a promise of hell, curse, or wrath. Some people said: It is the sin whose doer shall not be belief or was accompanied by the Prophet's saying: He is not one of us. As for minor sins, it was said: It is the sin where there is no prescribed punishment for it either in the world or in the Hereafter. Others said: Minor sins are every sin that was not accompanied by curse, wrath, or fire. It was said: Minor sins are the sins where there is no prescribed punishment or threat for them in the Hereafter; this is the most correct view: Minor sins are the sins which do not entail prescribed punishment nor a threat in the Hereafter.
2- Warning against sins and faults and not to underestimate any sin because when minor sins increase without expiation or their doer insists on committing them, they shall be his destruction.
3- Imam Ibn Al Qayyim (may Allah bestow mercy on his soul) said:
"Sins have destructive impact on the heart and the body in the world and in the Hereafter; of which are: Deprivation of a person from knowledge because knowledge is a light which Allah throws inside the heart, whereas sins put off that light.
Deprivation of sustenance.And a feeling of alieniation which a person finds in his heart between him and His Lord. This feeling cancels the pleasures of the world even if a person has all pleasures together. This feeling cannot be felt except by those whose hearts are vivid. If sins are to be left for this reason only, it will be enough. (3)
(1) Reported by Ahmad (1/ 446),
and Al Hafizh graded it as good. It was also reported in Fathul-Bary (11 /329) and Sheikh Al Albany said: It is authentic. See Hadith No. 2686 in Sahih Al Jami`.
(2) Fathul-Bary (11 /329).
(3) See the rest of these bad effects in Al Jawab Al Kafy [1/34].