As a general rule never take your whole fee in advance, nor any more than a small retainer. When fully paid beforehand, you are more than a common mortal if you can feel the same interest in the case, as if something was still in prospect for you, as well as for your client. And when you lack interest in the case the job will very likely lack skill and diligence in the performance.

Abraham Lincoln (1809-1865) American lawyer, politician, US President (1861-65)
Speech (1850), Notes for a Law Lecture (fragment)
    (Source)

No lecture of the sort given by Lincoln has been recorded. The date was assigned by Nicolay and Hay, with nothing concrete to contradict it. The lecture notes might well have been written several years later.