In Commander, if your commander is put into your hand by a spell, can you put it back into the command zone?

The Commander replacement effect applies whenever your commander would move from one zone to any other zone — including the hand. This is established in the Commander rules (CR 903.9a): if a commander would be put into its owner's hand, library, graveyard, or exile, that player may instead put it into the command zone.

This means that even if an opponent casts a spell like Chaos Warp, Evacuation, or Devastation Tide that would return your commander to your hand, you have the option to redirect that zone change and put your commander into the command zone instead. The choice is yours — you may also simply accept it going to your hand if you prefer.

The key word in CR 903.9a is 'may' — this is always an optional choice made by the commander's owner at the moment the zone change would occur. You are never forced to send your commander to the command zone.

Concrete example: Your opponent casts Evacuation, which returns all creatures to their owners' hands. Your commander (say, Atraxa) would go to your hand. At that moment, you may choose to redirect Atraxa to the command zone instead, where it can be recast for its commander tax later.

Note: The same applies to graveyard, exile, or library — CR 903.9a covers all non-battlefield destination zones uniformly.