Does Islam have a flag?

There are many narrations where the Allah's Apostle (salallahu alayhi wassalam) mentions "flag" like the following one: > Narrated Anas: > > The Prophet had informed the people of the martyrdom of Zaid, Ja'far > and Ibn Rawaha before the news of their death reached. The Prophet > said, "Zaid took the flag (as the commander of the army) and was > martyred, then Ja`far took it and was martyred, and then Ibn Rawaha > took it and was martyred." At that time the Prophet's eyes were > shedding tears. He added, "Then **the flag** was taken by a Sword > amongst the Swords of Allah (i.e. Khalid) and Allah made them (i.e. > the Muslims) victorious." **Sahih Al-Bukhari Book 64, Hadith 4307** Wiki says "An Islamic flag is a flag that complies with Islamic rules." My question is "Does Islam have a flag?" and "What are the rules for the flag?" Answers with scholarly opinion based on Qur'an and Hadith preferred.