Michtav M’Eliyahu (2:184) A tzadik decrees and G-d fulfills – It is obviously true that this does not mean that a tzadik can decree something which G-d doesn’t want. The explanation is that there are tzadikim for whom the whole world exists in their merit. That all that happens in the world is merely a means for us to learn from the conduct of these tzadikim how to elevate our service of G-d. What we learn from them is what preserves all of us from the lowest to the highest. That is what it means that because of their merit we live because we are mere utensils for the tzadik which enables us to see G-d’s great kindness in that \He freely sustains the entire world .So when a tzadik who is at this exalted level sees an issue which hides an aspect of G-d’s honor it is appropriate for him to ask G-d to withhold it even if it involves a change in G-d’s normal actions. This is what is meant by “a tzadik decrees and G-d fulfills."
Rav Tzadok (Tzedkas HaTzadik 2:87) No decree comes from the mouth of God except with the consent of the righteous of the generation (who are His court), as it is said in Idra Rabbah "The secret of God is for those who fear Him," and until they consent, no judgment is decreed for the world. And for this reason, one must guard against anything bad ever coming out of his mouth.Certainly everything is according to Justice