Morgoth's Ring, 2nd paragraph, page 210
The Eldar wedded for the most part in their youth and soon after their fiftieth year. They had few children, but these were very dear to them. Their families, or houses, were held together by love and a deep feeling for kinship in mind and body; and the children needed little governing or teaching. There were seldom more than four children in any house, and the number grew less as ages passed; but even in days of old, while the Eldar were still few and eager to increase their kind, Feanor was renowned as the father of seven sons, and the histories record none that surpassed him.

Morgoth's Ring, 3rd paragraph, page 210
The Eldar wedded once only in life, and for love or at the least by free will upon either part. Even when in after days, as the histories reveal, many of the Eldar in Middle-earth became corrupted, and their hearts darkened by the shadow that lies upon Arda, seldom is any tale told of deeds of lust among them.

Morgoth's Ring, 4th paragraph, page 210
Marriage, save for rare ill chances or strange fates, was the natural course of life for all the Eldar. It took place in this way. Those who would afterwards become wedded might choose one another early in youth, even as children (and indeed this happened often in days of peace); but unless they desired soon to be married and were of fitting age, the betrothal awaited the judgement of the parents of either party.

Morgoth's Ring, 5th paragraph, page 210
In due time the betrothal was announced at a meeting of the two houses concerned, and the betrothed gave silver rings one to another. According to the laws of the Eldar this betrothal was bound to stand for one year at least, and it often stood for longer. During this time it could be revoked by a public return of the rings, the rings then being molten and not again used for betrothal. Such was the law; but the right of revoking was seldom used, for the Eldar do not err lightly in such choice. They are not easily deceived by their own kind; and their spirits being masters of their bodies, they are seldom swayed by the desires of the body only, but are by nature continent and steadfast.

Morgoth's Ring, 1st paragraph, page 211
Nonetheless among the Eldar, even in Aman, the desire for marriage was not always fulfilled. Love was not always returned; and more than one might desire one other for spouse. Concerning this, the only cause by which sorrow entered the bliss of Aman, the Valar were in doubt. Some held that it came from the marring of Arda, and from the Shadow under which the Eldar awoke; for thence only (they said) comes grief or disorder. Some held that it came of love itself, and of the freedom of each _fea_, and was a mystery of the nature of the Children of Eru.

Morgoth's Ring, 2nd paragraph, page 211
After the betrothal it was the part of the betrothed to appoint the time of their wedding, when at least one year had passed. Then at a feast, again shared by the two houses, the marriage was celebrated. At the end of the feast the betrothed stood forth, and the mother of the bride and the father of the bridegroom joined the hands of the pair and blessed them. For this blessing there was a solemn form, but no mortal has heard it; though the Eldar say that Varda was named in witness by the mother and Manwe by the father; and moreover that the name of Eru was spoken (as was seldom done at any other time). The betrothed then received back one from the other their silver rings (and treasured them); but they gave in exchange slender rings of gold, which were worn upon the index of the right hand.

Morgoth's Ring, 3rd paragraph, page 211
Among the Noldor also it was a custom that the bride's mother should give to the bridegroom a jewel upon a chain or collar; and the bridegroom's father should give a like gift to the bride. These gifts were sometimes given before the feast. (Thus the gift of Galadriel to Aragorn, since she was in place of Arwen's mother, was in part a bridal gift and earnest of the wedding that was later accomplished.)

Morgoth's Ring, 4th paragraph, page 211
But these ceremonies were not rites necessary to marriage; they were only a gracious mode by which the love of the parents was manifested, and the union was recognized which would join not only the betrothed but their two houses together. It was the act of bodily union that achieved marriage, and after which the indissoluble bond was complete. In happy days and times of peace it was held ungracious and contemptuous of kin to forgo the ceremonies, but it was at all times lawful for any of the Eldar, both being unwed, to marry thus of free consent one to another without ceremony or witness (save blessings exchanged and the naming of the Name); and the union so joined was alike indissoluble. In days of old, in times of trouble, in flight and exile and wandering, such marriages were often made.