Related Rule
Israel
Practice relating to Rule 66. Non-Hostile Contacts between the Parties to the Conflict
Israel’s Manual on the Rules of Warfare (2006) states: “Many of the customs that are accepted today, such as … not attacking a messenger conducting negotiations … originate in the Middle Ages.” 
Israel, Rules of Warfare on the Battlefield, Military Advocate-General’s Corps Command, IDF School of Military Law, Second Edition, 2006, p. 10.
The Manual on the Rules of Warfare (2006) is a second edition of the Manual on the Laws of War (1998).