Jami at-Tirmidhi — The Book on Salat (Prayer) — Hadith No: 284
Translation
Ibn Abbas narrated:"Between the two prostrations, the Prophet would say: (Allahummaghfir li, warhamni, wajburni, wahdini, warzuqni). 'O Allah! Pardon me, have mercy on me, help me, guide me, and grant me sustenance