Words' meanings change through time, as the gap between denotation and connotation widens. Originally, condescend meant simply to come down, and in the sense provided by posts above, it can mean for someone of higher rank or esteem to talk to the "lower masses." Biblical verses were written during a time when societal ranks were believed to be divinely set, inevitable and unchangeable. In that sense, from the perspective of the person "coming down" to speak to the masses, condescending was seen as a virtue -- "Oh, thank you, kind sir, for honoring me by acknowledging that I am alive and worthy of your words!"
But another perspective is that of a member of the masses being spoken to. When such a person feels "he spoke to me in a condescending manner" it implies that the speaker perceived himself to be somehow "above" the person to whom he spoke, and as societies evolved toward embracing one another as equals, the idea of it being a "good" or "charitable thing" to step down to talk to someone "lower" has shifted to something along the lines of "who do you think you are for feeling you're better than I am, stepping off your pedestal to talk to me that way?"
