Definition and Context:
A call to mourning in the biblical context refers to a divine or prophetic summons for individuals or communities to express grief and repentance, often in response to sin, impending judgment, or calamity. Mourning in the Bible is not merely an expression of sorrow but is deeply connected to spiritual reflection, repentance, and a turning back to God.

Old Testament References:

1. Joel 1:13-14 : The prophet Joel calls the priests and the people to mourn due to a devastating locust plague, symbolizing a greater impending judgment. "Put on sackcloth and lament, O priests; wail, O ministers of the altar. Come, spend the night in sackcloth, O ministers of my God, for the grain offering and drink offering are withheld from the house of your God. Consecrate a fast, proclaim a sacred assembly; gather the elders and all the residents of the land to the house of the LORD your God, and cry out to the LORD."

2. Jeremiah 6:26 : Jeremiah urges the people to mourn as a response to the coming destruction from the north. "O daughter of my people, dress yourselves in sackcloth and roll in ashes. Mourn as for an only son, a most bitter lamentation, for suddenly the destroyer will come upon us."

3. Amos 5:16-17 : Amos describes a scene of widespread mourning as a result of God's judgment. "Therefore this is what the LORD, the God of Hosts, the Lord, says: 'There will be wailing in all the public squares and cries of 'Alas! Alas!' in all the streets. The farmer will be summoned to mourn, and the mourners to wail. There will be wailing in all the vineyards, for I will pass through your midst,' says the LORD."

New Testament References:

1. Matthew 5:4 : In the Beatitudes, Jesus pronounces a blessing on those who mourn, indicating a spiritual mourning over sin and the brokenness of the world. "Blessed are those who mourn, for they will be comforted."

2. James 4:8-10 : James calls believers to mourn as part of their repentance and humility before God. "Draw near to God, and He will draw near to you. Cleanse your hands, you sinners, and purify your hearts, you double-minded. Grieve, mourn, and weep. Turn your laughter to mourning, and your joy to gloom. Humble yourselves before the Lord, and He will exalt you."

Cultural and Religious Practices:

In ancient Israel, mourning was often accompanied by specific cultural practices such as wearing sackcloth, sprinkling ashes on one's head, fasting, and communal lamentation. These acts were outward expressions of inner sorrow and penitence. Mourning was not only a personal act but often a communal one, reflecting the collective responsibility and shared grief of the community.

Theological Significance:

A call to mourning serves as a reminder of the seriousness of sin and the need for repentance. It is an acknowledgment of human frailty and the consequences of turning away from God. Mourning, in the biblical sense, is a pathway to restoration and healing, as it leads individuals and communities to seek God's mercy and forgiveness. Through mourning, believers are drawn closer to God, experiencing His comfort and grace.