Last number is very difficult to read, therefore the dating is 1598 or 1599.
There has been some controversy as to whether this painting depicts the Preaching of John the Baptist or the Preaching of Christ. The Getty Museum and Ertz argue that this is Christ due to the yellow hallow around the head of the preacher. But the figure's short, ragged clothing indicates that it's meant to be John, as in the work by his father that this picture reinterprets.
The painting is in excellent condition: according to the Getty conservation report, the state of preservation is "nearly miraculous."
This painting may still have been owned by Jan at the time of his death, listed by his son as “Predicatie Christi, vol mannekens ende lanschap” and valued at fl.130. Denucé, Brieven en documenten, 70. That valuation does seem rather low for this painting, though -- but it would mean that Jan the Younger read the subject as the preaching of Christ. Another possibility is that the Getty painting is the “schilderye Lantschap Sint-Jans Predicatie gedaen by Jan Bruegel” (painting of a landscape with the preaching of St. John”) valued at fl. 300 in the inventory of Nicolaas Cornelis Cheeus in 1621-22: Duverger, Antwerpse Kunstinventarissen, vol. 2, 176. This valuation seems much more appropriate to the work in question. Cheeus's painting could also have been the Munich variant after his father's picture, though.