Mark’s Gospel emphasises the necessity of faithful discipleship; “follow me” is an important refrain from the beginning of Mark’s story. In three early scenes, the command of Jesus, “follow me”, is set forth (1:16–18; 1:19–20; 2:13–14). Jesus calls people to follow him. See https://johntsquires.com/2021/06/29/just-sandals-and-a-staff-and-only-one-tunic-mark-6-pentecost-6b/
The narrative of the beginning of the good news of Jesus the chosen one that ensues provides a sequence of events in which individuals, groups, and crowds all respond to this charge to follow Jesus. In this narrative, Jesus challenges people to respond to him with an active, informed discipleship; to leave the comfort of the familiar and set out, walking alongside him.

But following Jesus is not just about walking along beside him. The Gospel account makes it clear that followers are to step beyond Jesus, to walk out ahead of him, into unchartered territory. Following Jesus (discipleship) involves being sent forth (mission). And Jesus does this very thing with his followers. He sends them out, on mission.
Later in this narrative, leave Jesus and undertake his mission in the wider community (6:7–13). In this enterprise of mission, the disciples model their words and deeds on Jesus: “they proclaimed that all should repent…they cast out many demons and anointed with oil many who were sick and cured them” (6:12–13).
As they undertake this mission, the followers of Jesus are to be characterised by an ascetic mode of dress (6:8–9) as they undertake their public proclamation (6:10–11). And Jesus instructs them to “read the room” when they are welcomed into the houses in the villages and towns they visit. They are to be sensitive to the reception that they receive.
“So they went out and proclaimed that people should repent”, Mark reports (6:12). But with the caveat: “If any place will not welcome you and they refuse to hear you, as you leave, shake off the dust that is on your feet as a testimony against them.” So Jesus advises his followers (6:11). What did it mean, in the ancient world, to “shake the dust off your feet”?

Dust is central to who we are as human beings. The story of the creation of human beings indicates that the man was “formed from dust of the ground” before God breathed the breathe of life into him (Gen 2:7). But in the foundational myth that is told in the earliest chapters of scripture, dust is at the centre, also, of the punishments that are handed out after the sin committed by Adam and Eve.
The serpent, as a result of its role in tempting them, is told, “Because you have done this, cursed are you above all livestock and above all beasts of the field; on your belly you shall go, and dust you shall eat all the days of your life” (Gen 3:14; Isa 65:25).
The man is told, “By the sweat of your face you shall eat bread, till you return to the ground, for out of it you were taken; for you are dust, and to dust you shall return” (Gen 3:19).
Dust is used as a sign of cursing in various stories: in the plague of dust (Exod 9:8-10); in the ritual for cursing an unfaithful wife, when dust from the floor of the tabernacle is mixed into the water of bitterness (Num 5:11-31); in the destruction of the golden calf (Deut 9:21); and in various punishments by the Lord (Deut 28:24, Ps 78:27, Isa 25:12, 26:5, 2 Sam 22:43, 2 Ki 53:7, 2 Chr 34:4).
And the action of shaking out one’s clothing is integral to the scene in Nehemiah, where the leaders of the people who have returned to the land are required to “shake out their mantle” as a sign of their agreement to the economic arrangements made (Neh 5:13). Nehemiah warns them: “so May God shake out every man from his house and from his labour who does not keep this promise”. Shaking out has a sense of judgement, of being cursed by God.
However, in association with the tearing of clothes, the placing of dust on a person’s head is also a symbol of repentance. Joshua repents of the sin of Achan by tearing his clothes and placing dust on his head (Joshua 7:6). Ezekiel speaks of the people of Tyre, lamenting, as “they cast dust on their heads and wallow in ashes” (Ezek 27:30). Jeremiah reports that “ the elders of the daughter of Zion sit on the ground in silence; they have thrown dust on their heads and put on sackcloth; the young women of Jerusalem have bowed their heads to the ground” (Lam 2:20; see also Isa 25:12; 29:1–4).
The three friends of Job see him coming, and they “raised their voices and wept, and they tore their robes and sprinkled dust on their heads toward heaven”, before they then sat, grieving with him, “on the ground seven days and seven nights” (Job 2:12–13). Dust means mourning and repenting.
In like manner, after being raped by Ammon, Tamar put ashes on her head and tore her robe (2 Sam 13:19), as did Judas and his brothers when preparing for battle (1 Macc 3:47) and when they entered the ravaged temple (1 Macc 4:39).
The same actions involving dust are performed by Judas after being deceived by Simon (2 Macc 10:25), Jews at the news of Nicanor’s imminent invasion (2 Macc 14:15), and grieving daughters and mothers in Jerusalem when the victorious Ptolemy attempts to enter the temple (3 Macc 1:18). We might also note the messengers who arrive with torn clothes and dirt on their heads (1 Sam 4:12; 2 Sam 1:2, 15:32). These are all stories involving grief and despair.
Job himself uses dust and sackcloth to signify that “my face is red with weeping, and on my eyelids is deep darkness” (Job 16:15–16). As a result, he laments, “ God has cast me into the mire, and I have become like dust and ashes” (Job 30: 19). Returning to dust is the final state for those punished by God (Job 34:5; see also 10:9; 17:6; 20:11; 21:26; Ps 7:5; 22:15; 90:3; 104:29; Isa 26:5; Lam 2:21)—or, indeed, for all human beings (Eccles 3:20; 12:7).
In the end, though, Job “repents of dust and ashes” (42:6). He has had enough of being repentant. The book ends with a return of the defiant Job. He will have no more use for the dust and ashes of repentance.
In a number of scriptural incidents, dust is used in curses signalling divine punishment. Shimei, for instance, casts dust into the air to curse David (2 Sam 16:13). When Deutero-Isaiah speaks of the coming salvation that God will bring, to remove the punishment of exile, he exhorts Jerusalem to “shake yourself from the dust and arise” (Isa 52:2).
Dust had been a sign of the place of mourning, the place of despair, the place which signifies worthlessness and emptiness. Dust had been where the poor sat (1 Sam 2:8; Amos 2:7); it was where the enemies of Israel were pressed down and beaten into fine particles by the Lord (2 Sam 22:4 3; 2 Ki 13:7; Job 40:13; Ps 18:42; 44:24–25; 72:9; 83:13; Isa 41:2; Micah 7:17). Now, the people were called to leave that dust behind and move on in hope.
Jesus instructs his followers to shake the dust off their feet “as a testimony against them” (6:11). This seems to be an action warning the listeners that they are liable to judgement because they have failed to repent. However, the phrase could also be translated, “as a witness for their benefit”, suggesting that the action was intended to provoke the listeners to think further, after the disciples have left, about their message of repentance?
This latter sense is how the same construction functions earlier in Mark’s narrative, where the cleansed leper is to show himself to the priests “for a proof to them” (1:44). But later in the narrative, the very same phrase (eis martyrion autois) describes the function of the disciples defending themselves when on trial before “governors and kings” (13:9).
Could the action of shaking the dust off their feet signal that there would be hope, in the future, from the message of good news that the disciples proclaimed? The implication would be that this is the hope that they carry, and their “witness for the benefit” of their unwilling hosts is that this hope. This hope travels on with them as they journey onwards, with their proclamation of repentance. It also rests, along with the dust, with those they leave behind, who have not yet come to that point of repentance.
Or could the action of shaking off the dust have the function of warning recalcitrants—a graphic demonstration of the warning, ‘God will turn you to ashes if you do not repent’? As the disciples move on to the next town, they were leaving behind a warning with an implicit demand for their repentance.
That seems more likely to be the effect of the phrase, “as a testimony against them” (6:11). Certainly, that’s how it is understood in the parallel account in Matthew, where the action of shaking off the dust (Matt 10:14) is immediately followed by a reference to the fate experienced by Sodom and Gomorrah on the day of judgement (Matt 10:15).also ev
This is ident in the Lukan parallel, where a slight tweaking of the Greek makes it clear that this is understood as “a testimony against them” (Luke 9:5). Then, in the Lukan doublet of the sending out of the 72, the saying about the day of judgement (here referring only to Sodom) clarifies the expected judgement beyond doubt (Luke 10:12).
By implication from these later interpretations of the action, shaking the dust off the feet and moving on would appear to provide a sign of judgement to those who refuse to accept the message of the disciples, and repent.

Thanks for this exposition. Perhaps we in the UCA should give more attention to such texts as we have a poor record when it comes to hearing prophetic voices that challenge our self-image. Our ‘idealised self’ is way ahead of our ‘real self’. That in itself is not a problem if we paid attention to action-reflection processes; however, that is one of our weakest skills.