Jamieson, Fausset and Brown on 1 Thessalonians 1:8

8. from you sounded ... the word of the Lord--not that they actually became missionaries: but they, by the report which spread abroad of their "faith" (compare Ro 1:8), and by Christian merchants of Thessalonica who travelled in various directions, bearing "the word of the Lord" with them, were virtually missionaries, recommending the Gospel to all within reach of their influence by word and by example (1Th 1:7). In "sounded," the image is that of a trumpet filling with its clear-sounding echo all the surrounding places.

to God-ward--no longer directed to idols.

so that we need not to speak any thing--to them in praise of your faith; "for (1Th 1:9) they themselves" (the people in Macedonia, Achaia, and in every place) know it already.