“Rabbi Israel [Yisrael] Salanter (1810-1883) was very scrupulous in his observance of all the 613 mitzvot…It was his custom whenever Pesach came around, to personally supervise the baking of matzot in his town. He wished to make sure that it was done according to the time-honored halachah. On one such occasion, when he was confined by illness, his disciples volunteered to supervise the baking of the matzot.
‘Instruct us, Rabbi,’ they said. ‘Tell us all the important things we have to watch out for.’
‘My sons, see that the women who bake the matzot are well paid,’ was Rabbi Salanter’s brief reply’.” 
A similar story, possibly another version, comes from an authentic Musar source:
“Before Pesach, R’Yisrael was once unable to be present during the baking of his shmurah matzah, in which he was extremely meticulous. His disciples, who had undertaken to watch the baking in his place, asked him for directions. R’Yisrael instructed them to be extremely careful not to upset the woman who kneaded the dough and not to rush her, for she was a widow, and to upset her would [violate] the prohibition against oppressing widows and orphans.
‘The kashrut of the matzot is not complete…with hidurim in the laws of Pesach alone, but with the meticulous observance of the laws of behavior towards other people as well’.” 
As Rabbi Bonnie Margulis  of “Wisconsin Faith Voices for Justice” and others point out, “social justice” and “compassion” regarding fairness for the working person are essential Torah values:
“Do not take advantage of a hired worker who is poor and needy, whether that worker is a fellow Israelite or a foreigner residing in one of your towns. Pay them their wages each day before sunset, because they are poor and are counting on it. Otherwise they may cry to the Lord against you, and you will be guilty of sin.” 
Rabbi Margulis further comments:
“The Holiness Code of Leviticus 19 admonishes us – ‘The wages of a hired man are not to remain with you all night until morning’.  This command is given immediately after the admonishment – ‘You shall not oppress your neighbor, nor rob him.’ In this context, it becomes clear that failing to pay a worker right away is a form of oppression and the equivalent of robbing him.” 
If Rabbi Margulis points out Torah sources that require fairness in the treatment of the worker, Rabbi Yisrael Salanter makes emphatic that religious observance itself can’t be considered complete — or even legitimate in some cases — if workers are paid and/or treated poorly. Unleavened bread that is produced through unkind acts belies the very purpose of the mitzvah.
This ultimately echoes the pronouncements of Yishiyahu/Isaiah — especially the one read on Yom Kippur:
“Yet on the day of your fasting, you do as you please and exploit all your workers…
Is this the kind of fast I have chosen, only a day for people to humble themselves [insincerely]?
Is it only for bowing one’s head like a reed and for lying in sackcloth and ashes? Is that what you call a fast, a day acceptable to the Lord?
Is not this the kind of fasting I have chosen:
to loose the chains of injustice
and untie the cords of the yoke,
to set the oppressed free
and break every yoke?
Is it not to share your food with the hungry
and to provide the poor wanderer with shelter—
when you see the naked, to clothe them,
and not to turn away from your own flesh and blood?…
…and if you spend yourselves in behalf of the hungry
and satisfy the needs of the oppressed,
then your light will rise in the darkness,
and your night will become like the noonday.” 
How much clearer can it be, that the Divine Itself does not tolerate the oppression of workers?
While Yishiyahu was declaring this with regard to Yom Kippur, is it any less true of Pesach?
Social and economic justice are not the sum total of religious obligation or observance.
But no observance is complete or valid without them.
This justice is part of what Bernie Sanders speaks out for.
I might not agree with all of his positions — especially on Israel.
But there is no louder cry for fairness, justice and compassion to be heard in America today.
 based on the version of the story in:
Ausubel, Nathan, ed.; A Treasury of Jewish Folklore; © 1048 by Crown Publishers, NY; p. 105
[The editor of this anthology doesn’t cite his source for the story.]
 Zaitchik, Rabbi Chaim Ephraim; Sparks of Mussar: A treasury of the words and deeds of the Mussar greats; Ester van Handel, trans.; © 1985 by Pisgah Foundation, Jerusalem, Israel; p. 41-2
 Dvarim/Deut. 24:14-15
 Vayikra/Lev. 19:13
[“Love your neighbor as yourself” is declared only 5 verses later]
 from Yishiyahu/Isa. 58.