A divine promise paints a picture of an ideal, stable existence in the Promised Land, where the life cycle flows completely without tragic interruptions at its beginning or end. The commentators agree that this reality is not given freely. Instead, it serves as a direct reward for serving God and carrying out His will [רש״י, מזרחי, שפתי חכמים, גור אריה].
This reward includes protection from the inability to conceive [קאסוטו, ביאור שטיינזלץ], as well as from miscarrying or burying children during one's lifetime [רש״י, ביאור יש״ר, בכור שור, קאסוטו]. Some extend this to mean that a parent will not see their children die even when those children reach adulthood [רשב״ם]. Although these experiences are most naturally associated with women, as they are deeply felt by mothers [הטור הארוך, ביאור יש״ר], the blessing spans all living creatures, ensuring the health and fertility of livestock as well [אבן עזרא, הטור הארוך, ביאור יש״ר, קאסוטו]. On a natural level, the physical health and proper function of the reproductive system are direct results of God blessing the people's food and water supply [הטור הארוך]. On a national scale, preventing infertility and the loss of children guarantees the rapid population growth necessary to successfully conquer and fully settle the land [העמק דבר].
Beyond physical reproduction, there is also a spiritual dimension to this promise. It guarantees that scholars will not remain "infertile" in their teachings, but will successfully raise students to continue their path [פרדס יוסף, חתם סופר]. The privilege of raising both children and students allows an individual to pass down their heritage and repair the spiritual flaws of past generations [ספורנו].
The promise also guarantees a long life and a peaceful death at a good old age [ביאור שטיינזלץ, חזקוני]. The primary approach among commentators is that every person has a natural lifespan determined by their biology. However, people often die prematurely due to external elements such as wars, plagues, harsh climates, or poor choices. Remaining close to God grants a person special protection against these dangers, allowing them to safely reach the full potential of their natural years [אבן עזרא, ספורנו, הטור הארוך, ביאור יש״ר].
This completion of life involves profound divine precision. God fills the years of the righteous day by day and month by month, meaning they depart the world on the exact date they were born. There is a discussion regarding whether this simply means a person reaches their originally determined lifespan, or if their righteous actions cause God to grant them additional years beyond the initial decree [תורה תמימה]. Ultimately, while the lives of the wicked are cut short [בכור שור], the righteous are given the time to finish their purpose on earth. At the end of their complete days, just before passing, they are granted a vision of the spiritual reward waiting for them [קיצור בעל הטורים].