A.T. Robertson Commentary Hebrews 13:23

"Know ye that our brother Timothy hath been set at liberty; with whom, if he come shortly, I will see you." — Hebrews 13:23 (ASV)

Hath been set at liberty (απολελυμενον). Perfect passive participle of απολυω, to set free, in indirect discourse after γινωσκετε. Possibly from prison if he came to Rome at Paul's request (2 Timothy 4:11,21).

Shortly (ταχειον). Same comparative as in verse 19, "sooner" than I expect (?).