12 “Even now,” declares the Lord,
    “return to me with all your heart,
    with fasting and weeping and mourning.”

13 Rend your heart
    and not your garments.
Return to the Lord your God,
    for he is gracious and compassionate,
slow to anger and abounding in love,
    and he relents from sending calamity.
14 Who knows? He may turn and relent
    and leave behind a blessing—
grain offerings and drink offerings
    for the Lord your God.

15 Blow the trumpet in Zion,
    declare a holy fast,
    call a sacred assembly.
16 Gather the people,
    consecrate the assembly;
bring together the elders,
    gather the children,
    those nursing at the breast.
Let the bridegroom leave his room
    and the bride her chamber.
17 Let the priests, who minister before the Lord,
    weep between the portico and the altar.
Let them say, “Spare your people, Lord.
    Do not make your inheritance an object of scorn,
    a byword among the nations.
Why should they say among the peoples,
    ‘Where is their God?’”

What to do in the face of the impending calamity – this threatened invasion of a great army (1-11)? In today’s passage God speaks directly through His prophet, and calls for a national prayer meeting in which all ages are to come together before Him in genuine repentance (12-16). He is looking for the reality of repentance, and not just an outward, symbolic, ritualistic expression.

The appeal to God is on the basis of the Lord’s character (13b,14). It is also for the sake of the Lord’s Name (17).

I was thinking, ‘When did we last have a national call to prayer in the UK?’ Also reflecting, with sadness, that it is hard to imagine there being such a thing any time soon; when I found an article which begins like this:

”Four days after he became prime minister in May 1940, Winston Churchill approved a national day of prayer. Roused by news of the German onslaught against the British Expeditionary Force (BEF) in Belgium and France, people throughout Britain flocked to their local churches and chapels. Five days later, news reached the country of the successful evacuation of the British army from Dunkirk. Many laymen, as well as clergy, quickly attributed this as a ‘deliverance’ or ‘miracle’ to divine providence and to the day of prayer. Churchill himself became an enthusiast, approving two national days of prayer in each of the next three years. Then, in 1943 and 1944, he agreed to brief halts in war production so that factory and office workers could join in the BBC’s broadcast services.

This event is now probably the best known example of a custom that, in the British Isles, goes back to the tenth century when King Aethelred ordered prayers for God’s help to withstand a Danish invasion. Growing in number during the wars of Edward I, Edward II and Edward III, special acts of worship continued after the Reformation and were soon to become a settled tradition of public fasts and days of humiliation or thanksgiving.

Between 1535 and the last national day of prayer in 1947, there were 544 English and Welsh or British occasions, as well as 170 separately ordered Scottish and 84 Irish occasions. These extraordinary moments of special national worship are a register of great moments of crisis, anxiety and celebration in Britain’s past.” (https://www.historyextra.com/period/modern/praying-britain-national-day-prayer-history-when-deliverance/)