PTNed 39.b:22[2] :חד בר ^נש^ נדר דלא מרווחא ٠٠٠ אישתבעת אמ׳ ליה‏ : a certain person vowed not to make a profit. He said to him: What did you vow?
See the entire entry for šbˁ vb. C to swear