It appears as if Saul was reluctant for the killing to take place in David’s house. To that end, the men must watch the house for David to leave and then grab him. Exactly why Saul showed such a reluctance is unclear. Perhaps he wanted to speak with David before David was killed.
11 Saul sent messengers to David’s house to watch him, that he might kill him in the morning. But Michal, David’s wife, told him, “If you do not escape with your life tonight, tomorrow you will be killed.”