Halakhah zu Mischlej 19:18

It is from the roots of the commandment [that] since Israel are called the children of the Omnipresent, He, may He be blessed, wanted to discipline them for their sins, so that they return to Him and, in the end, merit the world that is completely good - and like the matter that is written (Proverbs 19:18), "Discipline your son while there is still hope, and do not set your heart on his destruction." And based on this principle, they, may their memory be blessed, said (Makkot 22b) that we estimate [the strength of] the one liable for lashes, such that he not die from the wound of the lashes. And they would lash him according to that which they appraised him that he can withstand from the flogging and not die. And even after they estimated him and started flogging him - if they saw they he is not able to withstand the estimate that they estimated about him, they leave him; as we say in the chapter [entitled] Elu Hen HaLokin in Tractate Makkot 22b, "[If] he is partially flogged and they saw that he is not fit to take that which they estimated about him, he is exempt."