That is also the area covered by Greater Syria, the term ISIS itself uses in its name. al Sham.
That use of the term Syria goes back to long before Mohammed or Christ.
“A country of southwest Asia on the eastern Mediterranean coast. Ancient Syria also included Lebanon, most of present-day Israel and Jordan, and part of Iraq and Saudi Arabia.”
http://www.thefreedictionary.com/Syria
Why in the world would ISIS use the term “Syria” in its modern day sense of referring to the lines drawn by France and Britain and imposed on the Arab world by them? The very reason for being of ISIS is to reject and destroy those boundaries. So if they use the word Syria, they don’t mean the modern country.
In 450 BC Herodotus wrote about a ‘district of Syria, called Palaistinê”, which is approximately modern Israel. So in ancient times Israel was considered to be part of Syria.