Trust, but verify

"Trust, but verify" (Russian: доверяй, но проверяй, romanized: doveryay, no proveryay, IPA: [dəvʲɪˈrʲæj no prəvʲɪˈrʲæj]) is a Russian proverb, which rhymes in Russian. The phrase became internationally known in English after Suzanne Massie, a scholar of Russian history, taught it to Ronald Reagan, then president of the United States, who used it on several occasions in the context of nuclear disarmament discussions with the Soviet Union.
Suzanne Massie, an American scholar, met with Ronald Reagan many times between 1984 and 1987 while he was President of the United States. She taught him the Russian proverb doveryai, no proveryai (доверяй, но проверяй) meaning 'trust, but verify'. She advised him that "The Russians like to talk in proverbs. It would be nice of you to know a few. You are an actor – you can learn them very quickly." The proverb was adopted as a signature phrase by Reagan, who used it frequently when discussing United States relations with the Soviet Union.
After Reagan used the phrase to emphasize "the extensive verification procedures that would enable both sides to monitor compliance with the treaty", at the signing of the Intermediate-Range Nuclear Forces Treaty, on 8 December 1987, his counterpart General Secretary Mikhail Gorbachev responded, "You repeat that at every meeting". To this, Reagan answered, "I like it". While Reagan quoted Russian proverbs, Gorbachev quoted Ralph Waldo Emerson, who had been popular in the USSR when Gorbachev was in college, saying that "the reward of a thing well done is to have done it."
Following the 2013 Ghouta attacks, Secretary of State John Kerry told a news conference in Geneva that the United States and Russia had agreed on a framework to dispose of Syria's chemical weapons. He said "President Reagan's old adage about 'trust but verify' ... is in need of an update. And we have committed here to a standard that says 'verify and verify'."
In 1995, the similar phrase "Trust and Verify" was used as the motto of the On-Site Inspection Agency (now subsumed into the Defense Threat Reduction Agency).
In 2000, David T. Lindgren's book about how interpretation, or imagery analysis, of aerial and satellite images of the Soviet Union played a key role in superpowers and in arms control during the Cold War was titled Trust But Verify: Imagery Analysis in the Cold War.
In 2001, the National Infrastructure Protection Center (NIPC), a national critical infrastructure threat investigation and response entity, published a paper entitled "Trust but verify" on how to protect oneself and their company from email viruses.
In 2015, both Democrats and Republicans invoked the phrase when arguing for and against the proposed Iran nuclear deal framework.
In the study of programming languages, the phrase has been used to describe the implementation of downcasting: the compiler trusts that the downcast term will be of the desired type, but this assumption is verified at runtime in order to avoid undefined behavior.
The phrase has been used in relation to India–China border disputes and also following the Galwan clash during the 2020 China–India skirmishes. Variants of the phrase were also reported in the Indian media, "distrust until fully and comprehensively verified", and "verify and still not trust".
On July 24, 2020, US Secretary of State Michael Pompeo referenced the proverb in a speech at the Richard Nixon Presidential Library saying that in dealing with China, the United States must instead "distrust and verify".
Nikolay Shevchenko of Russia Beyond writes that this saying must have been originated relatively recently. For example Vladimir Dal's vast collection Sayings and Bywords of the Russian people [ru] does not contain anything similar to the proverb. He noticed that both Vladimir Lenin and Joseph Stalin voiced similar ideas, but did not invoke the saying:
The sequel of the film A Great Life, A Great Life, 2 [ru] (shot in 1946 but shelved until 1958) uses the saying as it is.