You may want to read this :
https://bitcoin.org/en/developer-guide#standard-transactions .
Abstract.
If you create a redeem script, hash it, and use the hash in a P2SH output, the network sees only the hash, so it will accept the output as valid no matter what the redeem script says. This allows payment to non-standard pubkey script almost as easily as payment to standard pubkey scripts. However, when you go to spend that output, peers and miners using the default settings will check the redeem script to see whether or not it’s a standard pubkey script. If it isn’t, they won’t process it further—so it will be impossible to spend that output until you find a miner who disables the default settings.
~~MZ~~
