Both Uses

redeem
in
The Screwtape Letters
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The Enemy's human partisans have all been plainly told by Him that suffering is an essential part of what He calls Redemption; so that a faith which is destroyed by a war or a pestilence cannot really have been worth the trouble of destroying.†
Chpt 5 *
The earliest converts were converted by a single historical fact (the Resurrection) and a single theological doctrine (the Redemption) operating on a sense of sin which they already had—and sin, not against some new fancy-dress law produced as a novelty by a "great man", but against the old, platitudinous, universal moral law which they had been taught by their nurses and mothers.†
Chpt 23

Definitions:

(1) (redeem as in: its main redeeming quality is...)
to make up for something bad; or to save
(2) (redeem as in: redeem the coupon)
exchange, convert, or pay off
The exact meaning of redeem can depend upon its context. For example:
- "to redeem a coupon" -- exchange something for something else of value
- "to redeem stock" -- sell or convert to cash
- "to redeem a mortgage" -- pay off a loan
(3) (meaning too rare to warrant focus)
In Christianity, redemption is used to reference Jesus' sacrifice to make up for human sin.

Old usage (as might be found in the Bible or in Shakespeare) also uses redeeming time to refer to making the best use of time.