Declare his glory among the heathen - Among the nations; the people who are not Hebrews. The meaning is, Let it be proclaimed in all lands, among all people. Let it not be confined to those who are professedly his people, but let it be announced everywhere. This is copied literally from 1 Chronicles 16:24.
His wonders among all people - His “marvelous works;” those things which are suited to produce astonishment in the mind. The reference is to those works and doings of God which lie so far beyond the power of any created being, and which by their vastness, their wisdom, and their benevolence, are suited to produce a deep impression on the human mind.