Lamentations 2:18
Their heart cried unto the Lord, O wall of the daughter of Zion, let tears run down like a river day and night: give thyself no rest; let not the apple of thine eye cease. Their heart cried unto the Lord, O wall of the daughter of Zion, let tears run down like a river day and night: give thyself no rest; let not the apple of thine eye cease.
Jeremiah wrote it as part of a sad song commemorating the awful sufferings that came upon the apostate people of God, the inhabitants of Jerusalem. The chapter describes the tribulation suffered by the Jews under the Babylonians, which stands as a comparison showing that their suffering was not uniquely the greatest tribulation ever experienced. The suffering under the Babylonians was as great as the tribulation experienced when Jerusalem was destroyed by the Romans, so the destruction of Jerusalem by the Romans could not be the greatest tribulation in history described in Matthew 24.
Tears are the earnest response to the destruction and suffering of Zion's people, with grief to be poured out continually before God day and night without giving oneself rest. That lament is an example of sympathy for the misfortunes of others, calling believers to grieve for those in distress rather than focus only on their own hardships. Together with the watchman's commission to hear God's word and warn the house of Israel and with the truth that the soul that sins shall die and each bears his own iniquity, it applies to the duty to warn and train children and to cry to the Lord for them with tears day and night without rest.