One who steals a person from Israel is not liable until he brings him into his own domain. Rabbi Yehudah says: not until he brings him into his domain and uses him, as it is said "and he treated him as a slave and sold him" (Deuteronomy 24:7). And the first teacher does not require "use." Rav Acha son of Rava said: the case of "use" worth less than a perutah is the difference between them. Rabbi Yirmeyah inquired: if he stole him and sold him while the victim was asleep, what is the law? Rav Ashi inquired: if he sold a maidservant for the sake of the fetus she carries, what is the law? Let it be derived that there is no "use" at all here. No, it is necessary: the sleeping case is where he leaned upon him, and the maidservant case is where he stood her up against the wind. Is this the manner of "use" or is this not the manner of "use"? Let it stand unresolved.
When the Kidnapper Becomes Liable for Using His Captive
Yalkut Shimoni on Torah 329:2
הַגּוֹנֵב נֶפֶשׁ מִיִּשְׂרָאֵל אֵינוֹ חַיָּב, עַד שֶׁיַּכְנִיסֶנּוּ לִרְשׁוּתוֹ. ר"י אוֹמֵר, עַד שֶׁיַּכְנִיסֶנּוּ לִרְשׁוּתוֹ וְיִשְׁתַּמֵּשׁ בּוֹ, שֶׁנֶּאֱמַר (דברים כד, ז) "וְהִתְעַמֶּר בּוֹ וּמְכָרוֹ". וְתַנָּא קָמָא לָא בָּעֵי עִמּוּר אֲמַר רַב אָחָא בְּרֵיהּ דְרָבָא, עִמּוּר פָּחוֹת מִשְּׁוֵה פְּרוּטָה, אִיכָּא בֵּנַיְיהוּ. בָּעֵי רַבִּי יִרְמִיָּה, גְּנָבוֹ וּמְכָרוֹ יָשֵׁן, מָהוּ. בָּעֵי רַב אַשִּׁי, מָכַר שִׁפְחָה לְעוּבָּרָה, מָהוּ. תֵּפוּק לֵיהּ דְּלֵיכָּא עִמּוּר כְּלָל, לָא צְרִיכָא, יָשֵׁן, דְּזְגָא עֲלֵיהּ, שִׁפְחָה, דְּאוּקְמָהּ בְּאַפֵּי זִיקָא, דֶּרֶךְ עִמּוּר בְּכָךְ אוֹ אֵין דֶּרֶךְ עִמּוּר בְּכָךְ, תֵּיקוּ.