As is known, every contract has two parts, the body of the contract and the signature. The body of the contract details the specifics of the deal, while the signature indicates the final view of the owners and their agreement to what is written in the contract. So a deal cannot be finalized unless it is signed. In his sefer Olelos Ephraim (Vol. III, 460) the Kli Yakar uses this description to explain the great virtue of answering amen, and explains: The brachah is compared to the body of the contract, while answering amen is like the signature on it, and just like this signature fulfills and affirms what is written in the contract and brings it to completion, likewise, answering amen confirms and completes the brachah. (Olelos Ephraim Vol. III, 460)
