I do not believe that every single rule and ritual supposedly commanded by God in the Old Testament was actually of God. (Trying to distinguishing exactly which ones were and weren’t is not the focus of this comment.)
But I do believe that every single violent consequence for disobedience to those rules and rituals was never from God, but from that legalistic murderer, Satan, who was (and still is) sometimes confused with God.
For example, in the following passage I would argue that the Lord [God] speaks to Moses, but then the “Lord” [Satan] attempts to KILL Moses for failing to obey a rule (circumcision):
Exodus 4:22-26 NIV.
22 Then say to Pharaoh, ‘This is what the Lord says: Israel is my firstborn son, 23 and I told you, “Let my son go, so he may worship me.” But you refused to let him go; so I will kill your firstborn son.’”
24 At a lodging place on the way, the Lord met Moses and was about to kill him. 25 But Zipporah took a flint knife, cut off her son’s foreskin and touched Moses’ feet with it. “Surely you are a bridegroom of blood to me,” she said. 26 So the Lord let him alone. (At that time she said “bridegroom of blood,” referring to circumcision.)
(And note regarding verse 23: I believe the Lord had only told Moses to warn Pharaoh, not threaten him. Evil consequences to ignoring warnings are from the devil, not God.)
Thankfully, the devil was disarmed at the cross, when God nailed his weapon of dogma (“the rules and requirements of the law of Moses; carrying a suggestion of severity and of threatened judgment”) to it:
Colossians 2:14-15 (NIV)
14 having canceled the charge of our legal indebtedness [Greek: dogma], which stood against us and condemned us; he has taken it away, nailing it to the cross. 15 And having disarmed the powers and authorities, he made a public spectacle of them, triumphing over them by the cross.
Please consider this invaluable essay, which makes the case that even in the Bible, the devil was sometimes confused with God:
SATAN: Old Testament Servant Angel or New Testament Cosmic Rebel?