If a man will have a wayward and rebellious son, who does not listen to the voice of his father and to the voice of his mother, and they discipline him but he does not listen to them.
King David had a rebellious son, Avshalom, who not only rebelled against him personally, but also revolted against his kingship, and actually gained a popular following; ultimately seizing his throne. Nevertheless, despite the grave danger that David faced from Avshalom and his confederates, David sang praise to Hashem and expressed his confidence that Hashem will yet save him from his adversaries, and said the following.
Mizmor l'David b'vrocho mipnei Avshalom beno. Hashem, ma rabu tzarai rabim kamim alai... V'ata Hashem magen ba'adi kevodi umerim roshi. - A song of praise by David as he fled from Avshalom his son. Hashem, how numerous are my tormentors! Many rise up against me... But You, Hashem, are a shield for me and are my honor, and He who raises my head.
It is from these words of David, that the Gemara in Brachos (ז ע"ב) gathers how much pain a rebellious child brings upon his parents, and says as follows. A degenerate child in a person's home is an affliction more severe than the future war of Gog and Magog. [i.e. The suffering which a degenerate child brings upon his parents is more severe than the suffering which will be brought upon the Jewish People by the war of Gog and Magog, which will be fought before the advent of Mashiach, and will be the cause of much suffering]. We know this because the Passuk states, 'A song of praise by David as he fled from Avshalom his son'; and it is written immediately afterwards that David said with regard to his degenerate son Avshalom, 'Hashem, how numerous are my tormentors! Many rise up against me'. However, concerning the wars of Gog and Magog it is written, 'Why do people gather, and the nations talk in vain'; whereas 'how numerous are my tormentors' is not written there.
Rashi explains that the proof through which the Gemara proves that the war of Gog and Magog will bring about less suffering than that of a degenerate child, is from that which David says, 'Why do people gather, and the nations talk in vain', wherein David dismisses and makes light of the war of Gog and Magog, as if to say, 'Of what consequence is it to them?' It is from this assertion that we see that David deemed their military campaigns to be quite inconsequential.
Rashi's explanation is quite difficult to understand. For the Gemara clearly says, 'A degenerate child is an affliction more severe than the future war of Gog and Magog, for with regard to his degenerate son David said, 'Hashem, how numerous are my tormentors! While regarding the wars of Gog and Magog all David said was, 'Why do people gather, and the nations talk in vain'; whereas 'how numerous are my tormentors' he did not say'. This seems to clearly indicate that the Gemara proves this point, not from that which David said, 'why do people gather, and the nations talk in vain', but rather from the fact that David said 'how numerous are my tormentors' only in regard to his degenerate son but not in regard to the war of Gog and Magog.
Additionally, as the Maharsha asks, we need to understand the repetitive words of Dovid, 'How numerous are my tormentors! Many rise up against me'.
