Hadhrat Mufti Muhammad Taqi Usmani (may Allah preserve him) writes;  

“To love for the sake of Allah” means loving someone, not for any worldly gain, but because he is more religious and pious or he is very learned in Deen or is busy in serving the cause of Deen or because loving him or her is commanded by Allah, e.g. one’s parents.”

  “Easy Good Deeds”

Source: An excellent blog:at-Tazkirah: التذكرة