One who asks for advanced payment only does so on products or services he can guarantee. This would be impossible for a man and the Creator as "He is not even certain that he will be able to pay his old debts much less the new ones, man can meet his obligations ..only by means of the help that GD extends to him".
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Nefesh Hachaim
To make one's Torah study holy and pure he should reflect on his behaviors and confess on his sins before beginning to learn. His intention in learning should be that it will bring him closer to H'shem
Gate Four Chapter 6 pg 142
