Robert A. Guelich, "The Matthean Beatitudes: `Entrance-Requirements' or Eschatalogical Blessings?" JBL 95 (1976): 415-34.

For both Matthew and "Q," the beatitudes function as an eschatological pronouncement of the presence of the new age. If any indications in form and content suggest an ethical, "entrance-requirements" reading, they should be assigned to a pre-Matthean Sitz im Leben.