Commentary for Psalms 105:19

Until His word came [The word] of the Holy One, blessed be He, to fulfill His decree that the matter should “roll” and Israel should descend to Egypt.

the saying of the Lord purified him It tried Joseph, for he was tested and he overcame the temptation [to sin] with his master’s wife, and he was tortured because of her and purified with tortures to place him in the dungeon.