When Amos spoke, he was referring to David's tabernacle as an example, highlighting that Christ's original intention—the Gospel—was to reconcile both Jew and Gentile to Himself, putting to death the enmity between them.
Acts 15:13-18 - After they finished speaking, James replied, "Brothers, listen to me. Simeon has related how God first visited the Gentiles, to take from them a people for his name. And with this, the words of the prophets agree, just as it is written, 'After this I will return, and I will rebuild the tent of David that has fallen; I will rebuild its ruins, and I will restore it, that the remnant of mankind may seek the Lord, and all the Gentiles who are called by my name, says the Lord, who makes these things known from of old.'"