Shared ground
These lines portray the visible sky as a constant, public “announcement” about God. The “heavens” and the “expanse” are described as if they are actively reporting something: God’s “glory” (his greatness on display) and his “handiwork” (his skill as maker). That is an explicit claim of the poetry (v.1).
The message is pictured as unbroken. “Day after day” and “night after night” keep passing the report along, suggesting regularity and dependability, not a one-time sign (v.2).
At the same time, the passage insists this is not normal speech. It uses “speech” language and then immediately denies literal words and human language (v.3). The point is communication without sentences.
Where interpretation differs
A main question is what it means to say the sky’s “voice” is “heard” even though there are no words (v.3). Some take “heard” mainly as a metaphor for being perceived through sight and experience—people “get the message” by observing the sky. Others take “heard” as a stronger metaphor for a real, objective testimony that reaches all people, even if it does not come through human language.
A related question is how universal the claim is in v.3 (“where their voice is not heard”). Some read it as saying there is effectively no place on earth outside this witness; others read it as a poetic overstatement emphasizing broad reach, not a precise geography.
Why the disagreement exists
The poem mixes strong “speaking” verbs (“declare,” “pour forth,” “display”) with an equally strong denial of literal speech (“no speech nor language”). Because it is poetic person-like language, readers differ on how “literal” the universality and the “hearing” should be taken, and how tightly v.3 should be pressed.
What this passage clearly contributes
It presents creation—specifically the sky—as continuous evidence of God’s greatness and craftsmanship (v.1–2). It also frames that evidence as widely accessible and not dependent on any particular human language or messenger (v.3). The passage does not spell out a full message content beyond God’s glory/skill, but it does claim real “knowledge” is being conveyed (v.2) in a non-verbal way.
See also Romans 1:20 for a later biblical text that similarly argues that God’s power is perceived through what is made.