Brigham teaches that in the endowment one receives all the necessary ordinances to return back to the presence of God the Father.
Brigham Young, "Necessity of Building Temples-The Endowment," April 6, 1853, Journal of Discourses, 26 vols. (Liverpool : F. D. Richards, 1855), 2:31
But be assured, brethren, there are but few, very few of the Elders of Israel, now on earth, who know the *meaning* of the word *endowment*. To know, they must experience; and to experience, a Temple must be built.
Let me give you the definition in brief. Your endowment is, to receive all those ordinances in the House of the Lord, which are necessary for you, after you have departed this life, to enable you to walk back to the presence of the Father, passing the angels who stand as sentinels, being enabled to give them the key words, the signs and tokens, pertaining to the Holy Priesthood, and gain your eternal exaltation in spite of earth and hell.