Deuteronomy 15:1

מקץ שבע שנים AT THE END OF SEVEN YEARS [THOU SHALT MAKE A REMISSION] — One might think that this means seven years after each individual loan! Scripture, however, states, (v. 9) “[Take heed unto thyself lest there be in thy heart a word of worthlessness, saying], The seventh year … approacheth [and thine eye be evil against thy brother and thou givest him nought]”! Now, if you say that the seven years spoken of here mean seven years after each individual loan, i.e., after the granting of the loan to each individual person, how can one say, at the time the request for a loan is being made, “it (the seventh year) is coming near?” Consequently you must learn from this that Scripture means seven years according to the reckoning of the Sh’mitta-period (Sifrei Devarim 111:8).

מִקֵּ֥ץ שֶֽׁבַע־שָׁנִ֖ים תַּעֲשֶׂ֥ה שְׁמִטָּֽה׃

At the end of every seven years thou shalt make a release.