Inner peace comes from living with deep belief in the One God.
Re: The covenant with Allah:
"The covenant that Allah, may He be glorified and exalted, took from the progeny of Adam in the previous life
has not been erased from our memory and not one of the sons of Adam has forgotten it. If you want to ask about it, then we say to you: It is the fitrah (natural inclination/sound human nature) which is instilled in our souls and hearts, that drives us to believe in Allah and long to know Him, may He be glorified. In fact, it reaches the level of urgency that pushes and compels us to acknowledge that the Creator, may He be glorified and exalted, is the only, perfect Lord Who bestows His blessings upon us and upon all other created beings.
This spiritual and rational urge (to believe in Allah) is the strongest factor that prompts man to believe in Allah and affirm His Oneness, because it is usually stronger than any other impulses that may lead man to fall into ignorance and doubt. Often this urge (to believe) may overwhelm a person and make him realise the belief in divine Oneness (Tawheed) deep in his heart at times of crisis and calamity, even if the one who still has that sound natural inclination (fitrah) is pretending today to be an atheist. The call of Tawheed is still urging him from deep inside to believe, because of this natural inclination (fitrah) which is the first covenant taken from the sons of Adam."
for more on this topic:
https://islamqa.info/en/answers/248517/the-covenant-taken-from-the-sons-of-adam-is-the-fitrah
The Covenant - Agreement With Allah - Mufti Menk
1 min 33 sec video
Covenant With Allah - Nouman Ali Khan