Psalmów 51:5 Kabała: Zohar

and he was also called sin by King David in the verse: “and my sin is ever before me” (Ps. 51, 5). He is so called because he makes man every day to sin before his Master, never leaving him from the day of his birth till the end of his life.

It is here fitting to consider why Shimei, who was a scholar and a wise man, behaved to David as he did..The truth is that the words of insult and cursing which he uttered were not his own, but entered into his heart from another region (from heaven), for David’s benefit, that he might repent with a perfect repentance, with a broken heart and with many tears before the Holy One. Therefore David said: “The Lord hath said unto him, Curse David” (Ibid. 5, 10). He knew that the cursing and words of insult were inspired from above.