Many people; rather, many peoples. Shall go; or, set forth. The prophet means to represent the nations as encouraging one another on the way. There is no jealousy among them, for the "mountain" can hold them all.
He will teach us. The nations feel their ignorance of God, and their need of "teaching." God alone can teach them concerning himself (Romans 11:33, Romans 11:34; 1 Corinthians 2:10, 1 Corinthians 2:11); and "he will teach" them, either directly, as the Incarnate Son, or indirectly through those whom he has appointed to be "teachers" (1 Corinthians 12:28).
Of his ways; i.e. "some of his ways," not "all of them;" for at present "we know in part" only (1 Corinthians 13:9), and the greater portion of his ways are "past finding out" (Romans 11:33). The "ways" here spoken of are, no doubt, rules for the conduct of life, which are practically inexhaustible.
God, however, will teach every man, who honestly seeks to learn, enough to enable him to "walk in his paths." Out of Zion shall go forth the Law; rather, instruction, or teaching. The word (torah) is without the article.
The instruction intended is that of the Church of God.