The connection to the parasha seems obvious, since we are all familiar with the Midrash:
And it is immortalized in the piyut we say in musaf on Yom Kippur:
But this is not the פשט of the text. This is a diatribe by Amos against the injustice he saw in his own time, not in some long-distant past.
To better understand the connection, we have to understand who Amos was.
He was a Judean shepherd who was called to be the נביא of the destruction of Shomron, just as Jeremiah was the נביא of the destruction of Jerusalem and Samuel was the נביא of the destruction of Shilo. He was an older contemporary of Isaiah (who was a נביא in Judah at that time). His first prophecy starts with a short address to all the surrounding nations, and how ה׳ tolerated some of their sins but there was one that sealed each one’s fate:
Then he goes into the sins of Judah, with the same brevity that he addressed the other nations:
Then we have the bulk of his prophecy, against the kingdom of Israel. It is important to note the difference between Judah and Israel. For Judah, the final sin is על מאסם את תורת ה׳ וחקיו לא שמרו. For Israel, the final sin is על מכרם בכסף צדיק ואביון בעבור נעלים. As we have discussed in פרשת מצורע, there is a subtle dynamic in םפר מלכים between the kingdoms of יהודה and ישראל that חז״ל were sensitive to. יהודה and ישראל were complementary parts of what should have been a single nation. יהודה kept the בית המקדש but their בין אדם לחברו was lacking. ישראל worshiped עבודה זרה but were united and trusted each other:
And this is evident in the straw the broke each respective camel’s back. ה׳ could forgive Judah until they finally abandoned תורת ה׳, and could tolerate Israel’s עבודה זרה until they lost their sense of justice. It is this שנאת אחים that Amos saw that חז״ל saw foreshadowed in the sale of Joseph, that made the Midrashic connection between the two.
Rav Soloveitchik saw another parallel between the haftorah and the parasha:
And this was in fact Amos’s personal experience:
But both the history of Joseph that we see in the upcoming parshiot and Amos’s own message show that the will of ה׳ cannot be suppressed:
Coming back to the original theme of the injustice that the brothers did to Joseph, not only did it echo in the time of Amos, but it had repercussions throughout history: