The verb diaphulassō means to guard or protect with diligence and thoroughness — the dia- prefix intensifying the basic meaning of phulassō (to guard). It appears in Luke 4:10 in the devil's quotation of Psalm 91, promising that angels will guard Jesus completely.
The irony of Satan quoting Psalm 91's promise of angelic protection to tempt Jesus is profound. The same promise of God's comprehensive guarding that was meant to inspire trust is weaponized to tempt presumption. Jesus's response — refusing to test God — shows the difference between trusting God's protection and manipulating it. True faith rests in God's care without demanding divine performance on demand.