Ecclesiastes 7:4, “The heart of the wise is in the house of mourning, but the heart of fools is in the house of mirth.”
First off, for those who care about such things, this seems very likely to be a source for Tolkien’s statement that Olorin learned wisdom in the halls of Nienna.
Secondly, What is wisdom? Proverbs would tell us that it is the fear of YHWH, which is to say knowing Him for who He is and rightly responding to that knowledge (Prov. 9:10). So, wisdom is to know YHWH and rightly respond to YHWH.
Ultimately, True Wisdom—the Wisdom of God—is embodied in the Crucified Christ (1 Cor. 1:23-24). Christ crucified IS the Wisdom of God, He IS the character of God manifest perfectly within the context of fallen creation, such that to see the crucified Christ IS to see who God is toward His creatures and so IS to see Wisdom. Wisdom is known definitively at the cross—and the cross is indeed the “House of Mourning.”
If any is to be wise, let him go to this house; let him stand at the foot of the cross and see Wisdom in her unveiled beauty in the person of the crucified Lord; let him learn Wisdom here, let him understand the Holy One here, let him know here the truth that orders all things—let him be taught by the Crucified One in this holy House of Mourning.
And yet…..the moment one enters the House of Mourning on Calvary and realizes that, in this house, Wisdom is revealed and the Holy One is truly made known, in that very moment, the House of Mourning is itself revealed to be the House of Feasting (Ecc. 7:2). This is the house in which YHWH prepares a feast for his people (Is.25:6ff), in which Wisdom gives Himself as food and drink to any and all who would come (Is. 55:1-3), and in which the one whom to know is to know God offers His flesh and blood as Bread and Wine which to eat is to know God and so to live (John 6:35, 53ff + Prov. 9:5). Yes, when we recognize by the illumination of the Spirit that the Crucified Christ is Himself the revelation of the living God whom to know is Wisdom we see that the House of Mourning is itself the House of Feasting and that tears of mourning will become the wine of mirth.