Continuing on in Bossuet’s Elevations on the Mysteries, in this case 1,3 (the previous one is here):
I AM WHO AM. HE WHO IS, hath sent me to you. It is so that God defined himself. It is to say that God is he in which non-being has no place, who thus is always, and always the same; who thus is unchangeable: who thus is eternal: all terms which have no explanation of themselves. I AM WHO AM. And it is God who gives himself this explanation by the mouth of Malachi, when he said this through the prophet: For I am the Lord, and I change not.
God is thus an intelligence who cannot be ignorant of anything, neither doubt anything, neither learn anything, neither lose or acquire any perfection: for all of this is part of non-being. Now God is he who is, him who is by essence. How thus can one think that he who is, not be? Or that the idea which encompasses all being is not real? Or that, while one sees that the imperfect is, one could say, one could think, in hearing that which one thinks, that the perfect not be?
He who is perfect is happy, because he knows his perfection, for to know his perfection is a too essential part of perfection to miss being perfect. O God, you are happy! O God, I rejoice in your eternal happiness! All of the Scripture preaches that the man who hopes in you is happy. For a stronger reason, are you happy, yourself, O God, in whom one hopes. Also St. Paul calls him expressly happy when he said to Timothy (I Tim 1:11;6:15,16): I announce to you these things according to the glorious Gospel of happy God; and then, It is he who has shown you in his time he who is happy and the only powerful: King of Kings and lord of lords, who along possesses immortality and is clothed in an inaccessible light, to whom belongs glory and an eternal empire. O happy God, I adore you in your happiness. Be praised forever for having me to be acquainted and know that you are always and changelessly happy. Only you alone are happy and those who, knowing your eternal happiness, make it theirs. Amen. Amen.