Commentaries:
God laid His hands on Egypt in divine judgment by sending plagues. When trying a blasphemer, each witness placed his hands upon the guilty person to signify his acceptance of the verdict. Conversely, when a victim was spared death—as when God commanded Abraham not to sacrifice Isaac or when He allowed the leaders of Israel to see Him without dying—mercy is described as hands not being laid on the spared victim.
Martin G. Collins
Basic Doctrines: The Laying On of Hands