Genesis 50:3

And forty days were fulfilled for him; for so are fulfilled the days of those which are embalmed: and the Egyptians mourned for him threescore and ten days.

Forty days were fulfilled for him, for that is how many the days it takes to embalm. The Egyptians wept for him for seventy days.

And forty days were fulfilled for him; for so are fulfilled the days of embalming: and the Egyptians wept for him three-score and ten days.

and they fulfil for him forty days, for so they fulfil the days of the embalmed, and the Egyptians weep for him seventy days.

taking the forty days required to complete the embalming. And the Egyptians mourned for him seventy days.