1 Samuel 21:2

The king hath commanded me a business. This pretence of a private commission from the king was a mere invention, but his "appointing his servants to meet him at such and such a place" was probably the exact truth. After parting with Jonathan, David probably did not venture to show himself at home, but, while Saul still supposed him to be at Bethlehem, gave orders to some trusty officer to gather together a few of his most faithful men, and await him with them at some fit place. Meanwhile alone he sets out on his flight, and, having as yet no settled plan, goes to Nob, because it was out of the way of the road to Bethlehem, whither Saul would send to arrest him. Naturally such a visit would seem strange to Ahimelech; but David needed food and arms, and probably counsel; and. but for the chance of the presence of Doeg, no harm might have ensued. As it was, this visit of David completed the ruin of Eli's house.