Riyad as-Salihin 1325
Sahl bin Sa'd (May Allah be pleased with him) reported:
The Messenger of Allah (ﷺ) said, "Supplications at two times are never turned down (or said, "Are seldom turned down"), a supplication after the Adhan has been proclaimed, and a supplication during the battle combating the enemy." [Abu Dawud] .
وعن سهل بن سعد رضي الله عنه قال‏:‏ قال رسول الله صلى الله عليه وسلم ‏
"‏ثنتان لا تردان، أو قلما تردان‏:‏ الدعاء عند النداء وعند البأس حين يلحم بعضهم بعضًا‏"‏ ‏(‏‏(‏رواه أبو داود بإسناد صحيح‏)‏‏)‏‏.‏