墨迹未干 Ink not yet dry
Explanation
写字的墨迹还没有干。比喻协定或盟约刚刚签订不久（多用于指责对方违背诺言）。
The ink of the writing is not yet dry. It is a metaphor for a recently signed agreement or covenant, often used to blame the other party for breaking a promise.
Origin Story
话说两国交战多年，终于在一位德高望重的长老的调停下签订了和平协议。协议上写着：双方停止一切军事行动，从此永修睦邻友好关系。协议签订后，双方代表都郑重地签下了自己的名字，墨迹未干，其中一方就出兵侵犯了另一方。长老得知此事后，勃然大怒，痛斥他们出尔反尔，违背了刚刚签订的和平协议，全然不顾协议上墨迹未干的事实，最终导致了战争的再次爆发。
It is said that after many years of war between two countries, a peace treaty was finally signed under the mediation of a highly respected elder. The treaty stated: Both sides would cease all military actions and maintain friendly neighborly relations from then on. After the treaty was signed and the ink was still wet, one side attacked the other. When the elder learned of this, he was furious, rebuking them for their breach of faith and disregard for the recently signed treaty, ultimately leading to the outbreak of war again.
Usage
作谓语、宾语、定语；比喻事情刚发生不久就发生变化，多用于指责对方违背诺言。
Used as predicate, object, and attributive; It is a metaphor for the situation that something changes shortly after it happened, and it is often used to blame the other party for breaking the promise.
Examples
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合约墨迹未干，他们就反悔了。
heyue moji weigan, tamen jiu fanhuile.
The ink on the contract wasn't even dry before they went back on their word.
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这协议墨迹未干，他就违反了约定。
zhe xieyi moji weigan, ta jiuweifanzh le yueding
The ink on the agreement was barely dry, and he was already violating the agreement