Was this a new Nevu'ah?
Radak: No, it was in his first vision. First He told him that he will go where He sends him. Later, in the same Nevu'ah itself, he showed to him a Makel Shaked.
What is "Makel Shaked"?
Rashi: It is almond tree wood.
Rashi citing Targum Yonasan: It is a king that intends to harm.
QUESTIONS ON RASHI
Rashi writes that Makel Shaked is almond tree wood. What is the significance of this?
Rashi (12): Just like an almond tree sprouts flowers faster than all other trees, so I will rush to fulfill My word. Radak - this is a Siman of the punishments that will come on Yisrael quickly. It is called Shaked, for Shekidah is rapidity and effort - "Shaked Ani Al Davarai La'asoso" (verse 12), "Lishkod Al Dalsosai Yom Yom" (Mishlei 8:34).
Rashi (12, citing a Midrash): Just like an almond tree, from the time of planting until it fully ripens [the almonds] is 21 days, so is the number of days between the 17th of Tamuz, on which the city was breached, until Tish'ah b'Av, on which the Bayis was burned.
Rashi writes that there were 21 days between the breaching of the city on Tamuz 17 until Tish'ah b'Av. In Bayis Rishon, it was breached on the ninth (Melachim II, 25:3-4)!
The verse hints to Bayis Sheni. Then, there were 21 days in between. (PF)
Rashi is like the opinion in the Yerushalmi (Ta'anis 4:5) that also in Bayis Rishon, the breach was on the 17th; the verse in Melachim is based on a mistaken calculation 1 . (PF)
Refer to Melachim II, 25:4:1:2* .
