Short answer
– The human author of the book of Job (and therefore of Job 19:25) is not known. Among conservative evangelical traditions an early candidate often suggested is Moses, but many evangelical scholars simply treat the author as anonymous or a later Israelite “wisdom” writer. So the consensus in practical terms is: author unknown, with Moses sometimes proposed as the most-likely traditional candidate.

Why some evangelicals favor Moses
– Early Jewish and some Christian traditions attribute Job to Moses. That tradition has carried weight in conservative circles.
– Arguments offered in favor of Moses include perceived affinities with Pentateuchal language and theology, supposed familiarity with Egypt and the patriarchal world, and the idea that Moses would have both the education and the motive to preserve an early non‑Israelite wisdom story for Israel.
– Some conservative commentators who defend an early date for Job (i.e., patriarchal era or pre‑Monarchic) find Moses a convenient and plausible author because it fits a pre‑monarchy timeframe.

Counterpoints and alternative evangelical views
– Many evangelical scholars and study Bibles (ESV Study Bible, NIV Study Bible, etc.) say the author is unknown. Linguistic and literary features of Job’s Hebrew are distinctive and difficult to pin down to a specific period or person.
– Other proposals from conservative scholarship include a Solomonic or other wisdom‑school author, or an anonymous sage from the monarchy or even post‑exilic period. None of these proposals is universally accepted.
– Internal evidence (the setting in the land of Uz, the non‑Israelite context, the book’s complex poetic language and later editorial seams) means we cannot confidently name the author from the text alone.

How evangelicals use this in theology
– Regardless of the human author, evangelicals affirm that Job is part of God’s inspired Scripture and that verses like Job 19:25 (“For I know that my Redeemer lives…”) witness to a living, vindicating Redeemer. Many evangelicals read that verse as a messianic expression that is ultimately fulfilled in Christ.
– The anonymity of the human author does not undermine the theological weight of the verse; conservative expositors treat Job as canonical revelation that points forward to God’s redemption and eventual vindication of the righteous.

Further reading (evangelical resources)
– ESV Study Bible (notes on Job) — conservative study notes on date/authorship and theology.
– NIV Study Bible notes on Job.
– Commentaries by evangelical writers: Derek Kidner (Tyndale) and Tremper Longman III (various works on wisdom literature) discuss authorship issues and theological interpretation.

If you want, I can summarize the main arguments for and against Moses as author in more detail, or provide short evangelical commentary on Job 19:25 itself. Which would you prefer?