peace and quiet; safe and peaceful; tranquil and uneventful
A yojijukugo describing a state where nothing dangerous or troublesome happens; often used to wish for or report a calm, uneventful situation.
I hope you have a safe and peaceful journey.
May this year be tranquil and uneventful.
無事 means 'safety' or 'without incident' and is more common in everyday speech. 平安無事 is a more formal, four-character compound emphasizing both peace and safety.
平穏無事 is a near-synonym with a similar meaning, but 平安無事 is slightly more common and may carry a nuance of overall peace rather than just calmness.
A yojijukugo composed of 平安 (peace, tranquility) and 無事 (safety, without incident). The combination reinforces the idea of complete peace and safety.