Psalm 141:4

Psalm 141:3-4 (see also Matthew 6:13)
Set a guard, O LORD, over my mouth; keep watch over the door of my lips. Do not incline my heart to any evil thing, to practice deeds of wickedness with men who do iniquity; and do not let me eat of their delicacies. 

Isaiah 63:17: Why, O LORD, do You cause us to stray from Your ways and harden our heart from fearing You? Return for the sake of Your servants, the tribes of Your heritage.

Matthew 6:13: “‘And do not lead us into temptation, but deliver us from evil. [For Yours is the kingdom and the power and the glory forever. Amen.]’

Calvinists will sometimes try to find verses which show that God causes sin, in order to defend the notion that God causes whatsoever comes to pass, including sin, but yet is not guilty of being the Author of what He causes, because He has a noble purpose. But that is contradictory and unworkable. However, there is another explanation. Sometimes God will harden people’s hearts, but not by any magical process. For instance, with Pharaoh, all that God needed to do to harden Pharaoh’s heart was simply to allow him to think that he was getting away with something, or by allowing him to think that he was standing up to God, especially if God allows the Egyptian sorcerers to mimic Moses miracles. At the same time, God would have it that Pharaoh turn and obey Him. But due to Pharaoh’s heart, whether God does the miracles or not, it wasn’t going to change his heart. God knowing this, made use of him and allowed him to play the fool in thinking that he was getting away with something, and that’s what ultimately hardened Pharaoh and strengthened his resolve, and turned the whole episode into a powerful message to the world.

Davids perspective was that he wanted for God to search and try his heart, and to root out any evil within him: Search me, O God, and know my heart; try me and know my anxious thoughts. (Psalm 139:23) David had two major sins: An affair and a census. Perhaps thats why he wanted to make sure that he was in right standing with God, so that he didnt repeat prior mistakes. Scripture records that David was very cold in the death and murder of Uriah. If God doesnt expose him through the prophet Nathan, and does nothing at all, David could have remained cold and hardened indefinitely, and perhaps even more calculating. To incline his heart toward evil, all that God would have to do is nothing, complete non-action, giving him over to a depraved and reprobate mind. Gods exposure of him through the prophet Nathan actually set him on a new course of remorse and repentance. As an example, by not disciplining your child, through non-action, you are effectively inclining the child to evil. In fact, the Bible teaches that if you really love your child, youll discipline them. Non-action can be an action.

​Question: Why would we ask God not to incline our heart to any evil? Does that imply that God, at times, does move hearts to evil, or that He does give people over to a reprobate mind?

Answer: Notice the similarity of the Psalm 141:4 expression to that of a portion of the Lord’s prayer at Matthew 6:9-13: “Pray, then, in this way: ‘Our Father who is in heaven, Hallowed be Your name. Your kingdom come. Your will be done, on earth as it is in heaven. Give us this day our daily bread. And forgive us our debts, as we also have forgiven our debtors. And do not lead us into temptation, but deliver us from evil. [For Yours is the kingdom and the power and the glory forever. Amen.]

The context is about trusting in God’s provision (i.e. daily bread, forgiveness, deliverance, ect), and ultimately about seeking God, and being completely dependent upon Him. We know from 1st Corinthians 10:13 that God’s provision includes providing the “way of escape” from temptation. Obviously God does not tempt anyone, but God does test people’s faith. God can also harden people, as described at Jeremiah 18:1-13. If a child says to their father or mother, “Please help me not to be bad,” the parent is going to respond with reassurance. Therefore, I would imagine that that’s what’s going on, that is, acknowledging our fallen state before God, and acknowledging God’s power over it, and seeking reassurance from Him, to help overcome whatever obstacles that we may face.