Job 42:16 After this, Job lived a hundred and forty years; he saw his children and their children to the fourth generation.
The sense of the Hebrew is not clear in V16 as to whether Job was 140 years old when he died, or, lived another 140 years after the events recorded in the book of Job.
Scripture does not record the answer to this question but there have have been a number of suggestions which the Pulpit commentary summarizes.
Verse 16. - After this lived Job an hundred and forty years. It has been concluded from this statement, combined with that at the close of ver. 10, that Job was exactly seventy years of age when his calamities fell upon him ('Dict. of the Bible,' vol. 1. p. 1087, note); but this is really only a conjecture, since the statement that "God added to all that had been Job's to the double," does not naturally apply to anything but his property. We may, however, fairly allow that (as Professor Lee says) he "could scarcely have been less than seventy" when his afflictions came, having then a family of ten children, who were all grown up (Job 1:4). In this case, the whole duration of his life would have been 210 years, or a little more, which cannot be regarded as incredible by those who accept the ages of the patriarchs, from Peleg to Jacob, as respectively 239, 230, 148, 205, 175, 180, and 147 years. And saw his sons, and his sons' sons; i.e. his descendants
- grandchildren, and great-grandchildren. Even four gone-rations. According to the Hebrew inclusive practice of reckoning, we may regard his own generation as included.
Ellicott and Benson make similar remarks.