Then came David to Nob to Ahimelech the priest: and Ahimelech came to meet David trembling, and said to him, Why are you alone, and no man with you?
For example, the International Critical Commentary rejects the arrangement in this chapter, affirming that, "David had ample time to furnish himself for flight, after Jonathan bade him farewell,"[2] supposing that this journey of David to Nob must have happened that night when Michal let him down through the window.  Such is a worthless rearrangement.  On that night with Michal, David had all night until the next morning to have prepared for such a journey; and presumably from his own home would have been able not only to carry his sword, but also any provisions he wished to take.  Those could have been let down by Michal as easily as she let down David outside the city wall.  Besides that, Jonathan had specifically warned David in the preceding chapter, "Hurry!  Make haste; stay not."   (1 Samuel 20:38).  Therefore, it is just as logical to place the journey to Nob after  1 Samuel 20 as it is to place it after  1 Samuel 19.