Story of Puskara Tirtha is mentioned in detail in Shristi Khanda of Padma Purana.
When Savitri was late for Yajna, Brahma married a Gayatri at this Pushkara site. In anger, Savitri cursed all Gods and Goddesses. Savitri cursed the Brahma as follows:
145-148."If I have practised penance, if I have pleased my preceptors
in the groups of brahmanas, and at various places, brahmanas will
never offer you worship, except your annual worship (that falls) in
the month of Kartika which the brahmanas will (alone) offer, but not
other men at any other place on the earth.
So, people visit Pushkara during Kartika Masa.
Chapter 21, The Greatness of Puskara and Some Important Vows and subsequent chapters of Shristi Khanda describes greatness of Pushkara and Vows to be performed.
Benefits of Visiting Brahma tirtha or Pushkara Tirtha is mentioned in Chapter 129 of Reva Khanda- Avantya Khanda of Skanda Purana.
There at that Tirtha, Brahma, the most excellent one among Suras, the
grandfather of all the worlds, resorted to the banks of Narmada.
Merely by seeing him the Lord of Devas washes off the sins of the four
Varnas, committed earlier, including all mental and verbal ones and
those arising from activities of the body.
The eminent Brahmanas who take their holy bath and perform the
expiatory rites enjoined by Srutis and Smrtis have their residence in
heaven. Those who are oppressed by lust and greed and abandon the
scriptural texts and then prescribe expiatory rites (as they please)
fall into hell. A sinner should take his holy bath at the outset and
bow down to Brahma. Then he shall confess his sin. His sin perishes
quickly like darkness at sunrise.
He who takes his holy bath there in the Tirtha and adores Pitrs and
deities, derives the excellent benefit of Agnistoma Yajña. Whatever is
gifted away as Dana there at that Tirtha with Brahma in view, becomes
everlasting in its benefits.
If Japa is carried out merely of the Gayatri Mantra there, it shall
become as meritorious as one of the Rk, Yajus and Sama Vedas. There is
no doubt about it. If anyone were to cast off his body, usually very
difficult to be cast off, in the Tirtha there, his return from the
world of Brahma is undoubtedly impossible. He is honoured in Devaloka
for as many thousand years as there are bones of embodied beings in
the Brahma Tirtha.
Thereafter, he comes down into the world (here) and is reborn as one
knowing Brahman in a noble family. He shall be the most excellent one
among all the Varnas like the great deity among Devas. He will be
well-versed in all the lores and a master of the Vedas and their
Angas. He will be undoubtedly honoured in the world by kings.
He will be accompanied by sons and grandsons and will be free from all
ailments. By the power of Brahma Tirtha, he will live more than a
The noble souls who visit this meritorious Tirtha, the most excellent
one for those endowed with knowledge, a Tirtha that destroys all sins,