Reference for Sheviit 10:9

הַמַּחֲזִיר חוֹב בַּשְּׁבִיעִית, רוּחַ חֲכָמִים נוֹחָה מִמֶּנּוּ. הַלֹּוֶה מִן הַגֵּר שֶׁנִּתְגַּיְּרוּ בָנָיו עִמּוֹ, לֹא יַחֲזִיר לְבָנָיו. וְאִם הֶחֱזִיר, רוּחַ חֲכָמִים נוֹחָה מִמֶּנּוּ. כָּל הַמִּטַּלְטְלִין, נִקְנִין בִּמְשִׁיכָה. וְכָל הַמְקַיֵּם אֶת דְּבָרוֹ, רוּחַ חֲכָמִים נוֹחָה מִמֶּנּוּ:

One who returns the loan during the Sabbatical year, the spirit of the Sages is pleased by him. One who borrows from a convert whose family converted with him, need not repay his children. But if he did repay, the spirit of the Sages is pleased by him. All movable property is acquired through taking physical possession, but anyone who fulfills his word, the spirit of the Sages is pleased by him.

Jastrow