Huzoor S.A.W Said :
When a person told lie then Farishtey will go one mile far due to the bad smell of lie :....(Tirmizi :1972)
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If a person begans to tell single lie then his heart gets single black dot similarly if he continues to tell lie then his complete heart become dark heart..
How to remove black sins from heart
1.Remember about death
2.Read Quran As much as you can in allah house (Masjid)