Gyangeng Lhasang: Abundance Offering Coming from the Altruistic Mind
Here is an explanation from Geshe Thendar la about the puja and its benefits:
In the time of Guru Rinpoche in about 8th century AD there was a very powerful Dharma King in Tibet named Trisong Detsen. When he was going to build Samye Gompa there were many obstacles caused by spirit harm, such as naga gods and local gods or deities. In order to subdue the spirits, King Trisong Detsen invited Guru Rinpoche to Tibet to do some rituals. This was when the Lhasang Puja, the smoke offering for purification, was first performed.
Guru Rinpoche specifically composed the Gyangeng Lhasang Puja to cleanse and purify contamination of the spirits, local gods and naga gods, so that they could be healed in order to stop being mischievous and causing harm to the area and its people. After everything was purified and cleansed they were able to build Samye monastery.
During the Lhasang puja, all the guests should be invited: the guests of veneration: the Three Jewels (Buddha, Dharma and Sangha); the awakened manifestations of the Three Roots (Lama, Yidam and Dakini); the guests of qualities of the Oath Bound and Wisdom Protectors; and the guests of compassion. The puja should be dedicated to the beings of the six realms, especially the lower realms.
The puja is done because it is very auspicious and powerful and it really does remove many kinds of obstacles. It has that kind of strong power and potential and brings good luck to the place. It's very powerful. Because the puja is based directly on tantric practices, it becomes even more effective when the lama who is leading it has done a lot of meditation practice and has high realizations.
Normally when you offer the puja, it is good to do it on a Wednesday, which is the auspicious day for His Holiness. You can also offer it on other Dharma days and auspicious days. So basically it's a very powerful practice. It's good to do on special occasions.
In response to Kyabje Lama Zopa Rinopche's request to Geshe Thendar, the first Gyangeng Lhasang Puja for dispelling obstacles for FPMT projects was led on the 26th of June 2017 at Lawudo Gompa by 14 lamas and monks mostly from Thame, including Ngawang Ngendrak, Ngawang Dengyal, Ngawang Thokmay and others. In response to Rinpoche's request, a shorter version of the Lhasang Puja has been led monthly at Lawudo by Ngawang Ngendrak and a few other monks since then.
Translation of Geshe la's words and the puja title from Tibetan to English by Thubten Saldon, with light editing. Article by Simone Fry (Thubten Lhamo).