Both quotations taken from the transcript of LDS Perspectives Podcast Episode 55:Joseph Smith’s Use of Adam Clarke’s Commentary, released September 27, 2017
Thomas Wayment, the BYU professor who co-discovered the use of Clarke’s Commentary notes (emphasis added):
What we found, a student assistant (Hailey Wilson Lamone) and I, we discovered that in about 200 to 300 — depending on how much change is being involved — parallels where Joseph Smith has the exact same change to a verse that Adam Clarke does. They’re verbatim. Some of them are 5 to 6 words; some of them are 2 words; some of them are a single word. But in cases where that single word is fairly unique or different, it seemed pretty obvious that he’s getting this from Adam Clarke. What really changed my world view here is now I’m looking at what appears obvious as a text person, that the prophet has used Adam Clarke. That in the process of doing the translation, he’s either read it, has it in front of him, or he reads it at night.
We started to look back through the Joseph Smith History. There’s a story of his brother-in-law presenting Joseph Smith with a copy of Adam Clarke. We do not know whose copy of Adam Clarke it is, but we do know that Nathaniel Lewis gives it to the prophet and says, “I want to use the Urim and Thummim. I want to translate some of the strange characters out of Adam Clarke’s commentary.” Joseph will clearly not give him the Urim and Thummim to do that, but we know he had it in his hands. Now looking at the text, we can say that a lot of the material that happens after Genesis 24. There are no parallels to Clarke between Genesis 1–Genesis 24. But when we start to get to Matthew, it’s very clear that Adam Clarke has influenced the way he changes the Bible.