Chand Dekhne Ki Dua
On sighting the new crescent (hilal) — any month, especially Ramadan & Eid
اللَّهُمَّ أَهِلَّهُ عَلَيْنَا بِالْأَمْنِ وَالْإِيمَانِ، وَالسَّلَامَةِ وَالْإِسْلَامِ، رَبِّي وَرَبُّكَ اللَّهُ
Allahumma ahillahu 'alayna bil-amni wal-iman, was-salamati wal-Islam, rabbi wa rabbuka Allah.
Tarjuma Ae Allah! Is chand ko hum par aman aur imaan, salamati aur Islam ke saath tulu farma. Mera Rab aur tera Rab Allah hai.
O Allah, bring this crescent over us with security and faith, with safety and Islam. My Lord and your Lord is Allah.
Reference Jami' at-Tirmidhi 3451, narrated by Talhah ibn 'Ubaydillah (RA); graded hasan by Imam Tirmidhi. Also recorded by Ahmad and ad-Darimi.
Kab Aur Kyun Padhein
When the Prophet ﷺ saw the naya chand, he would read this short dua. It is the sunnah way to welcome every new lunar month, and it feels especially meaningful on the Ramadan and Eid crescent.
Read it whenever you spot the hilal in the evening sky. You are asking Allah to let the whole month pass in safety, iman, and peace.
Zaroori Baat
This chand dekhne ki dua is well attested in Tirmidhi. You will also see a very close variant with "bil-yumni wal-iman" (with blessing and faith) instead of "bil-amni" — both are transmitted wordings, so either is fine to recite. There is no fixed number of times; once, sincerely, is enough.