Yevamos 62a

Shkoyach, Reb Noach

The colloquial phrase "shkoyach" is a contraction of the Talmudic blessing "yeeshar kochachu" (your strength should be true), originally spoken by Hashem to Moshe. While commonly used today as a casual "thank you" or "good job," its literal status as a blessing can create halachic complications regarding Ribbis (forbidden interest). Because a borrower cannot offer a lender a gratuitous blessing, expressing "shkoyach" to a lender is technically problematic. However, modern Poskim like Rav Shlomo Zalman Auerbach and the Nesivos Shalom note that if the phrase is used reflexively as a standard polite "thank you" without the conscious intent of conferring a blessing, it is permitted.