must issue from the heart, must issue from within
must be acts of the heart
must be engaged in wholeheartedly
must be performed with a wholehearted engagement
etc.

A structural/stylistic note: The sentence لا ينالَ العبدَ منها إلا ما أقبل بقلبه عليه involves the use of the double negative, which is much more commonly used in Arabic than in English. There are many ways to handle that when translated into English. How you choose to handle it will depend on your style. In my examples above, I have completely skirted this issue, because I did not wanted to leave that to you. I only addressed the question of أقبل بقلبه عليه