The Messenger of Allah ﷺ said, "The keys to the unseen are five," then he recited, "Indeed, with Allah is knowledge of the Hour. He sends down the rain, and He knows what is in the wombs. No soul knows what it will earn tomorrow, and no soul knows in what land it will die. Indeed, Allah is All-Knowing, All-Aware." [Luqman 31:34]
حدثنا سليمان بن داود أخبرنا إبراهيم بن سعد عن الزهري ويعقوب قال حدثنا أبي قال حدثنا ابن شهاب عن سالم بن عبد الله
عن رسول الله ﷺ أنه قال مفاتيح الغيب خمس {إن الله عنده علم الساعة وينزل الغيث ويعلم ما في الأرحام وما تدري نفس ماذا تكسب غدا وما تدري نفس بأي أرض تموت إن الله عليم خبير}
Its isnad is sahih. Yaqub is Ibn Ibrahim bin Saad, one of Ahmad's teachers, whose reliability was already established at 1404 and 5974, and here we add Dhuhli's statement, "He and his brother Saad had both heard the books, but his brother died before he could write down very much from him, while Yaqub remained, so people wrote down narrations from him and found him to possess great knowledge." Ibn Saad said in Tabaqat 7/2/83, 84, "He was trustworthy and reliable, and he used to narrate the Maghazi and other material from his father, and the people of Baghdad heard from him. He was regarded as superior to his brother in excellence, piety, and hadith." This hadith is an abridgment of 5226, and see also 5579.