This niggun is sung by Chassidim in celebration of Yud Tes Kislev. This day marks the anniversary of the liberation, in 5559 (1798), of the Alter Rebbe, from his imprisonment in Petersburg, Russia, after being denounced by his opponents for his activities on behalf of Chassidus. The 19th of Kislev therefore symbolizes the victory of the Chassidic movement, especially of Chabad, which since then began to take root and spread throughout the Jewish world.
The lyrics are taken from Tehillim, chapter 55, verses 19-24. There Dovid Hamelech expresses his praise and thankfulness to the Creator, Who delivered him from the hands of his enemies, in answer to the prayers of his many friends who aided him and for whom he beseeches the A-lmighty to answer their requests. He implores the A-lmighty to punish the wicked. Dovid himself has absolute faith in the L-rd, who does not forsake the righteous.
As the Alter Rebbe was reciting these words of Tehillim he was redeemed from prison. It is therefore sung in celebration of his Chag Hageula. The same happened to the Mitteler Rebbe on Yud Kislev.