My word is my bond
From ACT Wiki
'My word is my bond' is the motto of the London Stock Exchange.
The motto is used to express and encourage adherence to the highest standards of integrity in financial markets.
Its origins include its use to create binding agreements without the need for written forms of contract.
In Latin - and on the London Stock Exchange's coat of arms - 'my word is my bond' is dictum meum pactum.