Shared ground
Paul ends this section by moving from instruction to prayer. The main point is stability: the community is not to be thrown off course by fear, rumors, or persuasive claims about “the day of the Lord.” Instead, they are to stay steady and keep what they already received from Paul’s team—teaching that came both in spoken instruction and in written form.
The prayer that follows is grounded in what God has already done. God is described as loving “us” and as the giver of “eternal comfort” and “good hope,” and these are explicitly said to come “through grace,” not as something earned. The requested outcome is comprehensive steadiness in both action and speech—“every good work and word.”
Where interpretation differs (only where needed)
One question is what “traditions” includes. Some read it mainly as core apostolic teaching (the message about Christ and basic moral instruction). Others think it also includes settled communal practices Paul taught alongside doctrine.
A second question is the scope of “by letter.” Some take it as referring only to letters from Paul and his coworkers to Thessalonica (or to the churches more broadly). Others ask whether it could point beyond Paul’s letters to later or wider written sources; the text itself does not specify.
A third question is how to understand the prayer’s addressees: “our Lord Jesus Christ himself, and God our Father.” Many readers see a joint appeal to both. Others think the wording primarily highlights unity in divine help while still directing prayer chiefly to the Father; again, the text’s grammar can be read either way.
Why the disagreement exists
The terms are broad and relational rather than highly defined. “Traditions” can mean a body of teaching, or teaching plus patterns of life. “Word” and “letter” describe channels of instruction without listing which messages or which documents. And the paired naming of Jesus Christ and God the Father compresses Christian confession and prayer language into a short closing, leaving some ambiguity about emphasis.
What this passage clearly contributes
Explicitly, the passage ties Christian steadiness to received instruction: what the community was taught is something to be kept, not reinvented under pressure. It also ties that steadiness to divine support: the God who loves and gives hope by grace is asked to strengthen the inner life (“hearts”) so that outward speech and behavior remain aligned with what is good (cf. good and word). Theologically, the text links faithful continuity (holding what was taught) with dependence (God establishing them), showing both as necessary parts of stability in a confusing moment.