C. F. Keil and Franz Delitzsch on Proverbs 29:14

Pro 29:14 14 A king who judgeth the poor with truth,      His throne shall stand for ever. בּאמת, as at Isa 16:5 (synon. באמונה, במישׁרים, במישׁור), is equivalent to fidelity to duty, or a complete, full accomplishment of his duty as a ruler with reference to the dispensing of justice; in other words: after the norm of actual fact, and of the law, and of his duty proceeding from both together. מלך has in Codd., e.g., Jaman., and in the Venetian 1517, 21, rightly Rebia. In that which follows, שׁופט באמת are more closely related than באמת דלים, for of two conjunctives standing together the first always connects more than the second. מלך שׁופט באמת דלים is the truest representation of the logical grammatical relation. To 14b compare the proverb of the king, Pro 16:12; Pro 25:5.