Why doesn't the Ring betray Sam in 🌋Mordor?

[ShardsofNarsil]

If the Ring is able to change sizes at its will (intentionally slipping off Isildur's finger), why does it not fall off Sam when he is surrounded by orcs?

 

[Starbrow]

Maybe it did change size, but Sam had his hand clenched, or in his pocket, or in some other position that prevented the ring from falling off his finger.

 

[PaigeSinclaire88]

If the Ring is able to change sizes at its will (intentionally slipping off Isildur's finger), why does it not fall off Sam when he is surrounded by orcs?

In my opinion, Hobbits are supposed to represent the meek, the innocent. And the reason why the ring doesnt corrupt Sam in Mordor is for the plain simple truth that it is possible that Sam is incorruptible. That Sam Wise has the purest heart of all the hobbits. Which is saying alot because it is Frodo that is on the "heros journey"