Hashem enjoys when a Tzadik nullifies his decrees:

Tzaddikim were given the power to nullify the decrees Hashem makes. This power was given by Hashem graciously, and he actually receives pleasure when his children nullify his decrees.[1] This is simialr to a father who gave over a novelty in Halacha or Torah and the son in his great depth and wisdom questioned it rightfully based on sources and reason. The father in this case is not only happy that his son has such depth of understanding, but actualy takes greater pleasure in his son’s refutal of his novelty than he does if his son were to simply acquiesce to it. The same applies with the Tzadik, that Hashem takes pride in the Tzadik’s tearing of his decrees. This is the meaning of the saying of the Sages “Tzadikim fulfill the will of Hashem” but not His words, as they actually contradict his words by making decrees which revoke it, but this in truth fulfills the will of Hashem.[2]

The creations must abide by the decrees of Tzadikim:[3]

Hashem stipulated with his creations that they must abide by the decrees of a Tzadik, even if they are asked to do something which is against their created nature. If the creation does not obey the decrees of a Tzadik it risks forfeiting its very existance. Thus, we find that Hashem told the reed sea by its inception of creation that it must split for the Jewish people when requested by Moshe and if it does not follow this instruction, it will become dry land. We also find that Pinchas Ben Yair once instructed a river to split for him in order so he can pass to fulfill a Mitzvah and the river argued that he is not required to do so being that he too is fulfilling Hashem’s will by not going against ist nature and splitting. Reb Pinchas threatened the river that if it does not split he will decree that the river become dry eternaly, and the river then split due to this threat. The power that Reb Pinchas held over the river was the G-d given stipulation to all creations that they must abide by the words of the Sages, otherwise they fear return to nothingness.

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[1] Or Torah [Maggid] Parshas Vayechi 59

[2] Or Torah [Maggid] Parshas Beshalach 89

[3] Or Torah [Maggid] Parshas Beshalach 89