There is a Misva to enhance the joy of a bride and groom at their wedding. The Tur (Rabbenu Yaakob Ben Asher Ba’al Ha’turim, Germany-Spain, 1270-1340) describes this Misva as a "Misva Gedola" – an especially important and valuable Misva.
Although the obligation applies to all people, there is a particularly strict obligation upon those who partake of the wedding feast. If a person is invited to the wedding, and he eats, drinks and enjoys but without doing anything to enhance the joy of the newlywed couple, as he simply eats and then leaves, then he disgraces the five "Kolot" ("sounds") that God mentioned in his blessing to the Jewish people – "There will once again be heard…in the cities of Judea and in the streets of Jerusalem, the sound of rejoicing, the sound of happiness, the sound of a groom, the sound of a bride, the sound of people saying: Give thanks to Hashem Seba’ot…" (Yirmiyahu 33:10-11).
This Misva is fulfilled through any means of bringing joy to a bride and groom. If a person is invited to recite one of the Sheba Berachot (seven special blessings) under the Hupa or after Birkat Ha’mazon, he fulfills the Misva of Simhat Hatan Ve’kala. This Misva is fulfilled even by going over to the bride and groom and engaging them in light, pleasant conversation. Bringing them food, drinks or something else that they need also fulfills this Misva. For example, it is common at weddings for the groom’s friends to bring him during the dancing a drink of water or a napkin to wipe his brow; this favor is part of the great Misva of Simhat Hatan Ve’kala. Praising the bride in the groom’s presence also fulfills the Misva, as he feels gratified having his choice of a bride confirmed.
A distinguished person fulfills the Misva of Simhat Hatan Ve’kala through his mere presence at the wedding. Bestowing honor upon the bride and groom is one way to fulfill this Misva, and when a prominent individual goes out of his way to attend the wedding, the bride and groom feel honored, and thus the Misva is fulfilled.
Of course, singing Pizmonim and other songs in the presence of the bride and groom also fulfills this Misva, as it enhances their feeling of joy and festivity.
It is customary to bring children to weddings in order to increase the festivity.
There is a Misva to praise the bride, specifically by describing her as "Na’a Va’hasuda" – "beautiful and charming." There is also a Misva to praise the groom.
Although there are certain restrictions on the use of live musical instruments after the destruction of the Bet Ha’mikdash, it is permissible and customary to play live music at a wedding celebration as part of the Misva of Simhat Hatan Ve’kala.
Summary: It is an important Misva to bring joy to the bride and groom at a wedding, and it is considered a grievous sin to partake of the wedding feast without participating in the celebration to enhance the couple’s joy. This Misva is fulfilled through any means of bringing them joy, such as complimenting them, showing them honor, speaking kind words to them, singing in their presence, bringing them things that they need, and so on.
