Al-Maruwidhi reported: Imam Ahmad ibn Hanbal, may Allah have mercy on him, was asked about love for the sake of Allah and he said, “It is that you not love him for the sake of some worldly benefit.”
Source: Ṭabaqāt al-Ḥanābilah 1/60
عَنِ المروذي قد سئل الإمام أحمد ابن حنبل رحمه الله عَنِ الحب فِي اللَّه فقال هو أن لا تحبه لطمع دنيا
1/60 طبقات الحنابلة