1)
How do we find 23 years from when Hashem first spoke to Yirmeyah?
1.
Rashi: Yoshiyah ruled for 31 years. Yirmeyah prophesized in 19 of them, i.e. all except for the first 12, and four years in Yehoyakim's reign.
2)
Why does it say "Ashkem" (future)?
1.
Rashi: This is present - I constantly rise early and speak.
2.
Radak: (It is like Hashkem.) Aleph is in place of Hei. Aleph, Hei, Vov and Yud are interchangeable. There is a Yud after the Tzeirei (under the Kaf); this is unusual.
