What is a Rainasbai Kirtan?

Rainasbai (ਰੈਣਿ ਸਬਾਈ; rainas baa-ee) means throughout the night. Rainasbai Kirtan (ਰੈਣਿ ਸਬਾਈ ਕੀਰਤਨ) refers to the singing of Gurbani throughout the night (dusk to dawn).

Bhai Gurdaas Ji mentions that the Great Bhagats held Rainsbais.

ਸੁਣਿ ਪਰਤਾਪੁ ਕਬੀਰ ਦਾ ਦੂਜਾ ਸਿਖੁ ਹੋਆ ਸੈਣੁ ਨਾਈ || ਪ੍ਰੇਮ ਭਗਤਿ ਰਾਤੀ ਕਰੈ ਭਲਕੈ ਰਾਜ ਦੁਆਰੈ ਜਾਈ ||
ਆਏ ਸੰਤ ਪਰਾਹੁਣੇ ਕੀਰਤਨੁ ਹੋਆ ਰੈਣਿ ਸਬਾਈ || ਛਡਿ ਨ ਸਕੈ ਸੰਤ ਜਨ ਰਾਜ ਦੁਆਰਿ ਨ ਸੇਵ ਕਮਾਈ ||
ਸੈਣ ਰੂਪਿ ਹਰਿ ਜਾਇ ਕੈ ਆਇਆ ਰਾਣੈ ਨੋ ਰੀਝਾਈ || ਸਾਧ ਜਨਾਂ ਨੋ ਵਿਦਾ ਕਰਿ ਰਾਜ ਦੁਆਰਿ ਗਇਆ ਸਰਮਾਈ ||
ਰਾਣੈ ਦੂਰਹੁੰ ਸਦਿ ਕੈ ਗਲਹੁੰ ਕਵਾਇ ਖੋਲਿ ਪੈਨ੍ਹਾਈ || ਵਸਿ ਕੀਤਾ ਹਉਂ ਤੁਧ ਅਜੁ ਬੋਲੈ ਰਾਜਾ ਸੁਣੈ ਲੁਕਾਈ ||
ਪਰਗਟੁ ਕਰੈ ਭਗਤਿ ਵਡਿਆਈ ||੧੬||
“Hearing of glory of Kabir, Sain also turned to be a disciple. In the night he would immerse in loving Devotion and in the morning he would serve at the door of the King. On one night some sadhus came to him and a Rainasbai was held, i.e. the whole night was spent in singing the Lord’s praises. Sain could not leave company of the saints and consequently did not perform the King’s service the following morning. God himself took the form of Sain. He served the King in such a way that the King was overjoyed. Bidding farewell to the saints, Sain hesitantly arrived at the palace of the King. The King from a distance the called him nearby. He took off his own robes and offered them to Bhagat Sain. ‘You have overpowered me’, said the King and his words were heard by one and all. God himself manifests the grandeur of the devotee.(16)”
(Vaar 10, Pauri 16)

The tradition of Rainsbai Kirtan is advocated in Sri Guru Granth Sahib Ji:

ਹਰਿ ਕੀਰਤਨੁ ਗਾਵਹੁ ਦਿਨੁ ਰਾਤੀ ਸਫਲ ਏਹਾ ਹੈ ਕਾਰੀ ਜੀਉ ||੩||
“So sing the Kirtan of the Lord’s Praises, day and night. This is the most fruitful occupation. ||3||”
(Ang 108)

ਸਹਜੇ ਗੁਣ ਗਾਵੈ ਦਿਨੁ ਰਾਤੀ ਕਿਲਵਿਖ ਸਭਿ ਗਵਾਏ ||
“In peace and poise, he sings the Lord’s Praises day and night, and all sins are eradicated.”
(Ang 768)

ਛੰਤ || ਭਿੰਨੀ ਰੈਨੜੀਐ ਚਾਮਕਨਿ ਤਾਰੇ ||
ਜਾਗਹਿ ਸੰਤ ਜਨਾ ਮੇਰੇ ਰਾਮ ਪਿਆਰੇ ||
ਰਾਮ ਪਿਆਰੇ ਸਦਾ ਜਾਗਹਿ ਨਾਮੁ ਸਿਮਰਹਿ ਅਨਦਿਨੋ ||
ਚਰਣ ਕਮਲ ਧਿਆਨੁ ਹਿਰਦੈ ਪ੍ਰਭ ਬਿਸਰੁ ਨਾਹੀ ਇਕੁ ਖਿਨੋ ||
ਤਜਿ ਮਾਨੁ ਮੋਹੁ ਬਿਕਾਰੁ ਮਨ ਕਾ ਕਲਮਲਾ ਦੁਖ ਜਾਰੇ ||
ਬਿਨਵੰਤਿ ਨਾਨਕ ਸਦਾ ਜਾਗਹਿ ਹਰਿ ਦਾਸ ਸੰਤ ਪਿਆਰੇ ||੧||
“Chhant: The night is wet with dew, and the stars twinkle in the heavens. The Saints remain wakeful; they are the Beloveds of my Lord. The Beloveds of the Lord remain ever wakeful, remembering the Naam, the Name of the Lord, day and night. In their hearts, they meditate on the lotus feet of God; they do not forget Him, even for an instant. They renounce their pride, emotional attachment and mental corruption, and burn away the pain of wickedness. Prays Nanak, the Saints, the beloved servants of the Lord, remain ever wakeful. ||1||”
(Ang 459)
The tradition of Rainasbai Kirtan was revived in the early 20th century by Bhai Sahib Bhai Randhir Singh.

Bhai Sahib Bhai Randhir Singh Ji doing Keertan in a Rainsbai Kirtan