International Standard Bible Encyclopedia
belsh: The primary idea of this word is "to gush forth" as a fountain. As used in Psalm 59:7 the thought is that these enemies had so cherished these evil thoughts and bitter wrath that now the heart is a very fountain of evil, and has taught the tongue how to give utterance thereto. But the previous verse shows that the Psalmist also had in mind the howling and barking of the dogs about the city. The imprecations of his enemies are like the snarling, howling, barking of dogs which in an eastern city makes the night hideous with the noise, and is continued until the daybreak.