The first hemistich occurs a little fuller in Proverbs 24:23, referring there, as here, to the administration of justice. For for a piece of bread that man will transgress. Thus translated, this clause confirms the former, and says that a judge given to favouritism will swerve from right under the smallest temptation.
But to bribe a judge with a morsel of bread seems an unlikely idea; and the gnome is of general application, "And for a morsel of bread a man [not 'that man'] will transgress." As some men in responsible positions are often swayed by low and unworthy considerations, so in social life a very insignificant cause is sufficient to warp the judgment of some persons, or draw them aside from the line of rectitude.
(For "a piece of bread," as denoting abject poverty or a thing of no value, see on Proverbs 6:26) The commentators cite Aul. Gell; 'Noct. Att.,' 1.15, "Frusto panis conduci potest vel uti taceat vel uti loquatur."
Septuagint, "He that regards not the persons of the just is not good; such a cue will sell a man for a morsel of bread."