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 ﷺ "ثنتان لا تردان، أو قلما تردان: الدعاء عند النداء وعند البأس حين يلحم بعضهم بعضًا" ((رواه أبو داود بإسناد صحيح)).