"Righteous and just is He": as it is written (Psalms 11:7) "For the L-rd is righteous and loves righteousness."
Variantly: "The Rock": the resolute one. "Perfect is His work": The work of His creatures is "whole" before Him. He delays the reward of the righteous and He delays the punishment of the wicked. The former take nothing (of their reward) in this world, and the latter take nothing (of their reward) in the world to come, as it is written (Devarim 32:34) "Is it (My reward) not laid up with Me, sealed in My stores (in the world to come)?" When do both receive (their punishment)?