Hi David,
The magnificent Chagall windows, depicting the twelve tribes of Israel, are located in the synagogue at the Hadassah Medical Center in Jerusalem.
The synagogue is open to visitors Sunday - Thursday during the hours: 8:00 am - 1:15 pm and 2:00 pm - 3:30 pm.
For more information on the windows and tours of the synagogue, offered by Hadassah, see this page from Hadassah's web-site.
http://www.md.huji.ac.il/chagall/chagall.html.
The hall in the Knesset displaying the Chagall tapestry can be seen during a visit to the Knesset. Tours of the Knesset are available Sundays and Thursdays between 8:30 am and 2:30 pm. For more information on reserving a spot on a Knesset tour, access to the Knesset, access phone numbers, and the Knesset visitors' dress code, please see: http://www.knesset.gov.il/tour/eng/evisit.htm.
Thanks for asking and enjoy your tours in Jerusalem.