The Prophet ﷺ said, "When the time of death approached the prophet of Allah Nuh ﷺ, he said to his son, 'I am going to relate my final testament to you. I command you with two things and forbid you from two things.I command you to declare that there is no god but Allah. If the seven heavens and the seven earths were placed on one side of a scale and "there is no god but Allah" were placed on the other, the side with "there is no god but Allah" would outweigh them. If the seven heavens and the seven earths were a sealed ring, "there is no god but Allah" would shatter them.And I command you to say, 'Glory be to Allah and praise be to Him,' for it is the prayer of every created thing, and through it creation is sustained.And I forbid you from associating partners with Allah and from arrogance...'" The hadith continues.
عن النبي ﷺ قال: إن نبي الله نوحا ﷺ لما حضرته الوفاة قال لابنه: إني قاص عليك الوصية: آمرك باثنتين، وأنهاك عن اثنتين، آمرك بلا إله إلا الله، فإن السموات السبع والأرضين السبع لو وضعت في كفة، ووضعت لا إله إلا الله في كفة، رجحت بهن لا إله إلا الله، ولو أن السموات السبع والأرضين السبع كن حلقة مبهمة قصمتهن لا إله إلا الله، وسبحان الله وبحمده، فإنها صلاة كل شيء، وبها يرزق الخلق. وأنهاك عن الشرك والكبر… الحديث
Ahmad narrated it (6583) from Sulayman bin Harb, who said, Hammad bin Zayd narrated to us, from Saqab bin Zuhayr, from Zayd bin Aslam, Hammad said, I think it was from Ata bin Yasar, from Abdullah bin Amr, and he mentioned the hadith. The discussion of it is set out in detail in the Book of Faith, in the chapter on Nuh's advice to his son not to associate anything with Allah.