Genesis 50:3

3 taking a full forty days, for that was the time required for embalming. And the Egyptians mourned for him seventy days.

Read Genesis 50:3 Using Other Translations

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 required for it, for that is how many are required for embalming. And the Egyptians wept for him seventy days.
The embalming process took the usual forty days. And the Egyptians mourned his death for seventy days.