An opening is not an obligation.
In the cave, Saul is exposed. David's men see a clean answer to a long danger: their enemy has walked within reach. David does cut Saul's robe, perhaps to prove how close he came. But the text says his conscience troubles him even over that small act. The closeness of power does not settle what power should do.
David does not deny that Saul has harmed him. He tells Saul that Saul is hunting for his life. Yet he refuses to make Saul's wrongdoing the final rule for his own conduct. He leaves judgment to the Lord and declines to strike Saul himself. The story's restraint is not passivity. It is a limit David places on his response.
Restraint holds when the test returns.
The second scene removes any claim that the cave was a one-time hesitation. Saul is asleep in a camp, surrounded by soldiers who are also asleep. Abishai offers to kill him with Saul's own spear. David again refuses. The chance is clearer, the pressure is direct, and David still draws the line.
David takes the spear and water jug instead. These objects show that Saul was vulnerable. David later calls from a safe distance, exposing the failure of Saul's guard while returning the spear. He does not need Saul dead to establish that he could have killed him. That distinction is the center of the story.
Restraint is not the same as trust.
Saul speaks warmly after both encounters. In the first, he calls David more righteous and asks him to protect his family line. In the second, he admits error and blesses David. The text records these words, but it does not ask David to put himself back within Saul's reach.
Each episode ends with separation. After the cave, Saul goes home while David goes to a stronghold. After the camp, David and Saul each go their own way. David's restraint does not require closeness, denial, or quick confidence. A person can refuse revenge and still keep distance from someone dangerous.