“And the ransomed of God shall return and come singing to Zion and everlasting joy shall be upon their heads; they shall obtain gladness and joy, and sorrow and sighing shall flee away” (Isaiah 51:11)
“Everlasting joy” is perpetual joy. It rests on our heads like a crown. The sefirah of crown represents the parts of the soul that are not conscious. For this reason, this verse is recited to remedy a bad dream, as dreams come from the not-conscious crown.
At the Giving of the Torah at Mount Sinai, the Jewish people merited two crowns. They lost them at the Sin of the Golden Calf. Our verse, however, indicates that those crowns will be restored in the future, “and everlasting joy shall be upon their heads” – the joy that is everlasting will once again return to our heads (Shabbat 88a). The removal of the crowns is like a bad dream. Their return is the dream’s remedy.
Actually, these crowns did not disappear, but were given to Moses. Thus, a person who feels connected to Moses connects – even now – to the ‘joy of the lost crown.’ In every generation, Moses has a successor, as chassidim say, “How happy are we and how goodly is our portion, that we are Jews, how pleasant is our lot that we merited to be the chassidim of our Rebbe.” This is a foretoken of the future joy of the crown.
Filling Our Mouths with Laughter
The name Isaac (Yitzchak) also means ‘he will laugh.’ After he was born, Isaac’s mother, Sarah, said “God made laughter for me, all who hear will laugh with me” (Genesis 21:6).
Isaac fulfills the adage to “serve God with joy.” This is also alluded to mathematically, since, “God made laughter for me, all who hear will laugh with me” (צְחֹק עָשָׂה לִי אֱ-לֹהִים כָּל הַשֹּׁמֵעַ יִצְחַק לִי) equals 4 times the value of “joy” (שִׂמְחָה).
There is a difference between joy and laughter: Joy is mainly in the heart, while laughter is external and visible to all. Laughter belongs to the future, as in the verse, “Then the laughter of our mouths will be full” (Psalms 126:2). Regarding the exile, the Talmud says, “It is forbidden for a person to fill his mouth with laughter in this world. (Berachot 31a). Isaac, however, belongs to the future. He lives in the present with the consciousness of, “then the laughter of our mouths will be full.”
It is worthwhile to contemplate the famous photograph of the Rebbe Rayatz, Rabbi Yosef Yitzchak of Lubavitch, in which he can be seen smiling “with a full mouth” – filling his mouth with laughter. All tzaddikim are happy, but there are tzaddikim who teach us to laugh, as well. They show us that the redemption is already here. Mashiach is right around the corner and it is already permissible to laugh, rejoice and sing with a full mouth, for God is with us.
 Isaiah 51:11.