Ibn ‘Umar reported God’s messenger as saying, "Supplication is beneficial regarding things which have happened and things which have not happened, so devote yourselves to supplication, servants of God."
Tirmidhi transmitted it, and Ahmad transmitted it from Mu'adh b. Jabal. Tirmidhi said this is a gharib tradition.
Jabir reported God’s messenger as saying, “No one offers a supplication without God bringing him what he asks or keeping away from him a like amount of evil, provided he does not ask for something sinful or for breaking ties of relationship.”