Sayyiduna Rafi' bin Khadij (may Allah be pleased with him) narrates: When the Prophet (peace and blessings be upon him) saw the new crescent moon, he would recite:
'Hilalu khayrin wa rushd'
(This is a crescent of goodness and right guidance.)
Then he (peace and blessings be upon him) would recite:
'Allahumma inni as'aluka min khayri hadha'
(O Allah, I ask You for its good.) He would recite this three times.
'Allahumma inni as'aluka min khayri hadhash-shahri wa khayril-qadar, wa a'udhu bika min sharrih'
(O Allah, I ask You for the good of this month and the good of destiny, and I seek refuge in You from its evil.) He would recite this three times.
Al-Tabarani recorded it, and its chain is hasan (good).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأذكار / 17147
Hadith Gradingمحدثین:إسنادہ حسن۔
Hadith Takhrij«أخرجه الطبراني فى المعجم الكبير (4409) ، أخرجه المعجم الكبير للطبراني برقم: 4409»