To the third day — That is, unto the next day, but one after the new moon. His meaning is not, that he would hide himself in any certain place all the three days, but that he would secure himself either at Bethlehem with his friends, or in any other place 'till the third day.
Related Commentaries of 1 Samuel 20:5
1 Samuel 20:5
5 And David said unto Jonathan, Behold, to morrow is the new moon, and I should not fail to sit with the king at meat: but let me go, that I may hide myself in the field unto the third day at even.