Chizkuni
ויהי כל ימי נח תשע מאות שנה וחמישים שנה וימת, “When Noach had reached the age of 950 years, he died.” You might ask that seeing we already know that Noach lived to become 950 years old, as the Torah had told us this in 7,11 and in the verse immediately preceding this one, so why did the Torah have to write this verse? The fact is that we might have added 7,11 and 9,28, and have arrived at the erroneous conclusion that Noach had lived 951 years. The Torah wished to inform us that the year in the ark was not considered as one of the years that Noach had “lived;” The author had already referred to that fact in chapter 9, verse 4.
