Gnomish
gretha-
verb. to save, rescue, preserve
reth-
verb. to save, rescue, preserve
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A verb appearing as gretha- “save, rescue, preserve” in the Gnomish Lexicon of the 1910s (GL/42), clearly based on the early root ᴱ√RESE [REÞE] (QL/79; GL/65). Elsewhere in the Gnomish Lexicon Tolkien had reth- “save, rescue, preserve”, but this variant was deleted (GL/65).
Neo-Sindarin: For purposes of Neo-Sindarin, I would updates these verbs to Fiona Jallings’s neologism ᴺS. reitha- “to rescue, save (from ruin, peril, loss)”, inspired by Q. rehta- of the same basic meaning.