Shulchan Arukh, Orach Chayim Siman 599
Can copy this into an AI, or connect the whole library to your assistant. For deeper learning, you can directly use the original seforim, sites, and apps.
ליל ראש השנה שחל להיו' במוצאי שבת אומרים ותודיענו:
Mishna Berura Yomi
When the night of Rosh HaShanah falls on Motza'e Shabbat, we say "Toda'inu."