Mustadrak al-Hakim — Hadith 3349

It is narrated from Sayyidah Aishah (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) said: "Had Allah Almighty shown mercy to anyone of the people of Nuh, He would have shown mercy to the mother of the child." Then he (peace and blessings be upon him) said (narrating the event): "Sayyiduna Nuh (peace be upon him) remained among his people for a thousand years less fifty (nine hundred and fifty years), calling them to the truth, until at the end of his time he planted a tree. When it had grown very large and sturdy, he cut it down and began making a ship from it. People would pass by and ask him (in astonishment), and he would say: 'I am making a ship.' At this they would mock him and say: 'Are you making a ship on dry land?! How will it sail?' He said: 'You will soon know.' Then when he had finished preparing it, the oven gushed forth ('and the oven gushed forth') and water increased in the streets. The mother of the child feared for his life, for she loved him intensely, so she took him and set out towards the mountain until she reached a third of it. Then when the water reached her there, she took him further up until she stood at the top of the mountain. Then when the water reached her neck, she lifted the child up with her hands (to save him from drowning), until the water swept them both away. So had Allah shown mercy to any of them, He would have shown mercy to the mother of the child." [Surah Hud: 40]
This hadith has a sahih (authentic) chain, but the two Shaykhs (Bukhari and Muslim) did not record it.