citation supporting his/her/its statement
Here is one:
Josephus Antiquities of the Jews — Book II Chapter 9.
Concerning the afflictions that befel the Hebrews in Egypt, during four hundred years. (21)
1. Now it happened that the Egyptians grew delicate and lazy, as to pains-taking; and gave themselves up to other pleasures, and in particular to the love of gain. They also became very ill affected towards the Hebrews, as touched with envy at their prosperity. For when they saw how the nation of the Israelites flourished, and were become eminent already in plenty of wealth, which they had acquired by their virtue, and natural love of labour, they thought their increase was to their own detriment. And having in length of time forgotten the benefits they had received from Joseph; particularly the crown being now come into another family; they became very abusive to the Israelites; and contrived many ways of afflicting them: for they enjoyned them to cut a great number of channels for the river, and to build walls for their cities, and ramparts, that they might restrain the river, and hinder its waters from stagnating, upon its running over its own banks: they set them also to build pyramids: (22) and by all this wore them out, and forced them to learn all sorts of mechanical arts, and to accustom themselves to hard labour. And four hundred years did they spend under these afflictions: for they strove one against the other which should get the mastery. The Egyptians desiring to destroy the Israelites by these labours; and the Israelites desiring to hold out to the end under them.