Reference : Hisn al-Muslim 202

بارَكَ اللهُ لَكَ في أَهْلِكَ وَمالِك، 
إِنَّما جَـزاءُ السَّلَفِ الْحَمْدُ والأَداء
Bārakallāhu laka fī ahlika wa mālik, 
innamā jazā'us-salafi ‘l-ḥamdu wa‘l-adā'.


May Allah bless you in your family and your wealth, 
surely the reward for a loan is praise and returning (what was borrowed).

Reference:
An-Nasa'i, 'Amalul-Yawm wal-Laylahp. 300, Ibn Majah 2/809. See also 
Al-Albani, Sahih Ibn Majah2/55.

Chapter: To the debtor when his debt is settled