Charles Spurgeon Commentary 2 Samuel 15:27-30

"The king said also unto Zadok the priest, Art thou [not] a seer? return into the city in peace, and your two sons with you, Ahimaaz thy son, and Jonathan the son of Abiathar. See, I will tarry at the fords of the wilderness, until there come word from you to certify me. Zadok therefore and Abiathar carried the ark of God again to Jerusalem: and they abode there. And David went up by the ascent of the [mount of] Olives, and wept as he went up; and he had his head covered, and went barefoot: and all the people that were with him covered every man his head, and they went up, weeping as they went up." — 2 Samuel 15:27-30 (ASV)

David probably wept partly because of his troubles, but also because of his sin, which the thought of his troubles no doubt brought to his mind, and especially that sin which he has so deeply deplored in the seven penitential Psalms, and most of all in Psalm 51. He wore no royal robe on this pilgrimage of sorrow, and he went barefoot up the slopes of Olivet.