iOS 9.2.1 (build 13D15) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2016-01-19T17:59:49Z. The update package is 1.1 GB. This is a delta (partial) update that requires 8.1.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: b3c25848bcd1b46e7348d773c2cb71ce94e214f5.zip.