I often hear people say that “the poor in spirit” in Matthew’s Beatitudes is about the spiritually poor. I am not sure that this is right. I wrote a blog post about this some time ago (which can be found by clicking here.) Today I came across Craig Keener’s commentary, which has some good stuff on this.
The expression “poor in spirit” (5:5) [sic] refers not to those with a deficit of moral righteousness (see 5:20), … Because the oppressed poor became wholly dependent on God (Jas 2:5), some Jewish people used the title as a positive religious as well as economic designation (1QM 11.9, 13; 13.14; 14.7; …). Thus it refers not merely to the materially poor and oppressed, but to those “who have taken that condition to their very heart, by not allowing themselves to be deceived by the attraction of wealth” (Freyne 1988: 72). Although Matthew does not stress renunciation of possessions to the same degree as Luke, for him as well the kingdom belongs to the powerless of the world, to the oppressed who embrace the poverty of their condition by trusting in God rather than favors from the powerful for their deliverance. (Emphasis added)
Source: Craig Keener, The Gospel of Matthew (Grand Rapids: Eerdmans, 2009), 168–9.