Ibn Ezra on Leviticus 19:16

רכיל. כמו רכולתך מכל אבקת רוכל והטעם המלשין כי הרוכל מעתיק יקנה מזה וימכור לזה והרכיל יגלה לזה מה ששמע מזה: A TALEBEARER. The word rakhil (talebearer) is similar to rekhulltekh (thy merchandise) (Ezek. 26:12) and rokhel (merchant) in With all powders of the merchant (Cant. 3:6). Rakhil means a slanderer, for the merchant moves goods. He buys from one person and sells to another. The talebearer reveals to one person what he heard from another person.

לא תעמד על דם רעך. שלא יתחבר עם אנשי דמים וידוע כי כמה נרצחו ונהרגו בעבור המלשינות ודואג האדומי לעד: NEITHER SHALT THOU STAND IDLY BY THE BLOOD OF THY NEIGHBOR. A person should not join bloodthirsty men.⁵⁸Literally, men of blood, persons who resort to violence to gain their end. See Prov. 29:10. It is known that many people have been murdered and killed because of slander.⁵⁹Hence Neither shalt thou stand idly by the blood of thy neighbor follows the law prohibiting tale-bearing. Doeg the Edomite⁶⁰Doeg told King Saul that Achimelech, the kohen of Nob, fed David. This resulted in the destruction of the city of Nob. See I Sam. 22:19. is proof of this.

וטעם אני ה׳‎. רואה מה שאתה עושה בסתר: The meaning of I am the Lord is, I see what you do in secret.