Will taking unpaid leave hurt tenure process?
Taking an unpaid leave of absence would often factor into tenure decisions. I would begin a discussion with you department head today. Express your concerns. COVID-19 is a very unique circumstance. Surely they could find a way for you to teach remotely if you start a discussion right now.
If I was a department chair, I would be finding ways to accommodate my faculty. But I would also want to have that discussion as soon as possible.
What you definitely do not want to do is wait until a month into the semester to inform your department that you are not going to be showing up. (We had a professor do this a few years ago and he was obviously fired).