ENOfficial
Aḥabbaka ‘lladhī aḥbabtanī lah. May He for Whose sake you love me, love you. Reference: Abu Dawud 4/333. Al-Albani graded it good in Sahih Abu Dawud 3/965.
Source: sunnah.com
Other translations
Arabic
أَحَبَّـكَ الّذي أَحْبَبْـتَني لَه
sunnah.com