Every word of the Torah is replete with profound messages. The pasuk in Tehillim 37:18, “Hashem knows the days of the innocent and their inheritance shall be forever” is interpreted by the Talmud in Bava Basra 58a as referring to the lives of the righteous. Just as the righteous are perfect, so are their days perfectly complete. Sarah Imeinu’s life was the essence of perfection. How can we define a perfectly complete life?
Horav Boruch Sorotzkin z.l., explains that before a person is born, his life-span has been pre-determined. A halachic rule governs the determination. One half day is viewed as a whole month, and one month in a year is considered an entire year. Consequently, one may be considered to have lived a whole year even if in fact he had lived only a part of it. This method of calculating time applies, regrettably, to those who do not utilize every minute of every hour to its fullest potential. One who does not value time may see his own time “cut short.” The righteous, however, who arrange for every minute to be spent wisely, are given the full year allotted to them. Sarah Imeinu attained perfection. Her temimus enabled her to live the “complete” life allotted to her.