Short answer
It has no basis in the sunnah. Chhatti is a South Asian custom held on the sixth day after birth. Hanafi scholars in the subcontinent advise against it, especially when it is treated as necessary or includes rites from other religions. The sunnah for the seventh day is aqiqah, shaving the head and naming.
Customs around birth are permissible only if free of haram and not treated as religion. A set sixth-day ritual held as necessary, or containing rites borrowed from other faiths, music or waste, is to be avoided. A simple family meal with no such beliefs is not haram.
The four schools agree on this.
Explanation
Chhatti (from the word for six) is a custom in parts of India, Pakistan and Bangladesh. Practices vary: bathing the mother and baby, dressing the baby in new clothes, a gathering of women, songs, special food and gifts. Many trace it to a pre-Islamic local rite, and it is not mentioned in the sunnah.
The Prophet ﷺ said that whoever introduces into our religion something that is not from it, it is rejected, and he warned against imitating the rites of other faiths. For birth, he gave a clear sunnah: the aqiqah, shaving and naming on the seventh day.
How Hanafi scholars judge it:
- Avoid it when people think it must be done, when there is fear of bad luck if it is missed, or when it includes rites of another religion, music, free mixing or debt.
- Allowed: family visiting the mother, gifts for the baby, or a meal, on any day, without ritual meaning.
- Better: put the effort and money into the aqiqah on the seventh day, which gives the same family gathering with reward.
For the sunnah way see what to do when a baby is born and the aqiqah day. For new-baby parties in the West see baby showers.
The evidence
Sahih Muslim 1718
Sahih... من أحدث في أمرنا هذا ما ليس منه فهو رد ...
"Whoever introduces into this matter of ours what is not part of it, it is rejected."
Rituals presented as religion need a basis in the sunnah.
Sunan Abi Dawud 4031
Graded hasan sahih... من تشبه بقوم فهو منهم ...
"Whoever imitates a people is one of them."
Rites borrowed from other faiths are to be avoided.
Sunan Abi Dawud 2838
Graded sahih... تذبح عنه يوم سابعه ويحلق ويسمى ...
"It is slaughtered for him on his seventh day, his head is shaved and he is named."
The sunnah sets the seventh day, not the sixth.
Where the ruling is recorded
- Radd al-Muhtar (Ibn Abidin), Kitab al-Udhiyah, closing discussion on aqiqah. The sunnah acts after birth are tied to the seventh day.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.