It is characteristic of Hebrew poetry to rhyme (so to speak) thoughts rather than sounds. This is called “Hebrew Parallelism.” To oversimplify: it is the practice of repeating the thought of the first line in the second. Thus, the writer expresses the same thought in different words.
This is very common in the Psalms.
Thus, one line of a poem will often comment on another: expanding or clarifying the meaning.
אַשְׁרֵי שֹׁמְרֵי מִשְׁפָּט עֹשֵׂה צְדָקָה בְכָל־עֵת
“How blessed are those who keep justice,
Who practice righteousness at all times!” (NASB)
Again, the Psalms are pointing us to the Way of Blessedness. Psalm 1 has tipped us off that this is the major theme of the whole book of Psalms. This is not conceived in the typically popular-religion terms of Salvation: where the whole point of faith is just meeting the terms of Eternal Life. This is about living in the realm of present blessing. This is about the life of faith.
יִשְׁלַח מִשָּׁמַיִם וְיוֹשִׁיעֵנִי חֵרֵף שֹׁאֲפִי סֶלָה יִשְׁלַח אֱלֹהִים חַסְדּוֹ וַאֲמִתּוֹ
“He will send from heaven and save me, he will put to shame those who trample on me. Selah. God will send forth his steadfast love and his faithfulness.” (NRSV)
My first reading of this is: “God will send help from far away.” And, there is some basis for this reading. But, that’s not the whole story.
In the Jenni-Westermann Theological Lexicon of the Old Testament we read:
Heaven often appears as the dwelling place of Yahweh and his hosts…, so that he also acts from heaven (e.g., Deut 4:39; 10:14; 26:15; 1 Kgs 8:23, 30, etc.; Isa 63:15; 66:1; Psa 2:4; 11:4; 20:7; 89:12; 102:20; 115:3, 16; Lam 3:41, etc….).” The Lexicon quickly adds that even Heaven itself is, of course, not adequate to either contain or constrain God. “As God’s resting place, heaven naturally belongs to the cultically pure realm (cf. Exod 24:10; …). Heaven is not able to contain God, however, because he stands beyond any cosmic boundary (1 Kgs 8:27; 2 Chron 2:5; 6:18; cf. Jer 23:24).