Psalm 100 is one of the brief, joyful “psalms of praise.” The verses you named (Psalm 100:4–5) read in most English translations along the lines of:

“Enter his gates with thanksgiving, and his courts with praise; give thanks to him and bless his name. For the LORD is good; his steadfast love (chesed) endures forever, and his faithfulness (emet) to all generations.”

Who wrote it?
– The psalm itself is anonymous in the Hebrew text — there is no superscription attributing it to David, Asaph, the sons of Korah, or anyone else. That means the original author’s name was not preserved in the canonical text.
– From an evangelical perspective there are two common (not mutually exclusive) approaches:
1. Respect for the biblical text’s anonymity: many evangelicals simply accept that the human author is unknown while affirming the psalm’s divine inspiration. The Spirit-breathed authority of the passage does not depend on knowing the human composer.
2. Liturgical/temple authorship: many conservative commentators suggest the psalm was composed by a Levitical musician or temple worship leader for corporate worship because of its vocabulary and structure (“enter his gates…his courts”), its short, hymn-like form, and its emphasis on thanksgiving and covenant faithfulness. Some traditions (and less formal devotional usage) have sometimes assumed Davidic authorship, but the text itself makes no such claim.

Why that view is common among evangelicals
– Evangelicals typically give weight both to the historical-linguistic clues in the text (which point to a liturgical setting) and to the confession that Scripture is God-breathed regardless of whether the human author is named.
– The psalm’s key Hebrew words — chesed (steadfast love/mercy) and emet (truth/faithfulness) — are covenantal terms used throughout Scripture. Evangelicals read these words as pointing to God’s unchanging, covenantal character ultimately fulfilled in Christ, which gives the lines enduring theological and worship significance.

Theological and practical emphasis (evangelical application)
– The psalm is used as a call to worship: come into God’s presence with thanksgiving and praise, acknowledging his goodness.
– Theologically it emphasizes God’s goodness, everlasting lovingkindness, and faithfulness across generations — attributes evangelicals connect to God’s covenant promises and the saving work of Christ.
– Practically it is often used as a call to corporate worship, in personal devotion, and in evangelistic invitations to trust God’s steadfast love.

Bottom line
– Psalm 100:4–5 has no named human author in the biblical text. From an evangelical standpoint the strongest case is that it was an inspired liturgical hymn—likely composed by a temple/Levitical worship leader — and its theological message is fully authoritative regardless of the anonymous human composer.