God can use a “non-prophet” to teach a truth which we don’t want to hear including “curses of judgment upon Israel itself”; there’s “no” partiality with God.

A Blessing only holds with respect to obedience. The rest is up to God’s Mercy.

To quote:

“Then Amos answered and said to Amaziah: “I was no prophet, nor a prophet’s son, but I was a herdsman and a dresser of sycamore figs. But the Lord took me from following the flock, and the Lord said to me, ‘Go, prophesy to my people Israel.’ 16 Now therefore hear the word of the Lord. “You say, ‘Do not prophesy against Israel and do not preach against the house of Isaac.’ Therefore thus says the Lord: “Your wife shall be a prostitute in the city and your sons and your daughters shall fall by the sword and your land shall be divided up with a measuring line; you yourself shall die in an unclean land and Israel shall surely go into exile away from its land.” (Amos 7:14-17)