Because of a trifle (because of a nail, a thing of no value) the city of Beitar was destroyed / to spoil the ship for a ha'porth of tar
Figuratively: Because of gossip or hatred among brothers, a great disaster was caused. (Literally: Because of a wheel-axle of a carriage or litter, Beitar was destroyed. The origin is in the story related below.)
("Because of Kamtza and Bar Kamtza Jerusalem was destroyed, because of a rooster and a hen Mount Gerizim was destroyed, because of an axle of a carriage Beitar was destroyed" – Gittin 55b. Also: (Translation) They used to, when a boy was born, hang a cedar tree, and for a girl, a cypress. At weddings, they would cut down the trees and make a canopy. Once, the Caesar's daughter passed by and the pin in her carriage broke. Her servants cut down a cedar and fixed the carriage. The Jews came, attacked them, and beat them. The servants reported to the Caesar: "The Jews have rebelled against you." He marched against them – Translation of Gittin 57a. Also: "And you will weep bitterly and cry: Oh God of my father, because of an axle of a carriage Beitar was destroyed, and two barley seeds destroyed my home" – Gordon, "Axle of a carriage," poems of J.L. Gordon.)
Translation
Expression (Hebrew)
אַשָּׁקָא דְּרִיסְפֵּק חָרֵב בֵּיתָר
Definition (Hebrew)
בְּהַשְׁאָלָה: בִּגְלַל הַלְשָׁנָה אוֹ שִׂנְאַת אֲחִים נִגְרַם אָסוֹן גָּדוֹל (מִלּוּלִית: בִּגְלַל צִיר שֶׁל מֶרְכָּבָה אוֹ אַפִּרְיוֹן חָרְבָה בֵּיתָר. הַמָּקוֹר בַּסִּפּוּר הַמְּסֻפָּר לְהַלָּן).
("אַקַּמְצָא וֶבֶּר קַמְצָא חָרוּב יְרוּשָׁלַיִם, אַתַּרְנְגוֹלְא וְתַרְנְגוֹלְתָּא חָרוּב טוּר מַלְכָּא, אַשָּׁקָא דְּרִיסְפֶק חָרוּב בֵּיתָר"- גִּטִּין נה ע"א, וְכֵן:"(תַּרְגּוּם) נוֹהֲגִים הָיוּ כְּשֶׁנּוֹלַד תִּינוֹק שָׁתְלוּ אֶרֶז, תִּינֹקֶת- שָׁתְלוּ שִׁיטָה. וּבִשְׁעַת נִשּׂוּאִים הָיוּ קוֹצְצִים אֶת הָאִילָנוֹת וַעֲשָׂאוּם חֻפָּה.פַּעַם אַחַת עֲבֵרָה בַּת הַקֵּיסָר וְנִשְׁבְּרָה יָתֵד בְּמֶרְכַּבְתָּהּ. קִצְּצוּ עֲבָדֶיהָ אֶרֶז וְתִקְּנוּ הַמֶּרְכָּבָה. בָּאוּ הַיְּהוּדִים, וְנָפְלוּ עֲלֵיהֶם וְהִכּוּם. הָלְכוּ וְאָמְרוּ לַקֵּיסָר: מָרְדוּ בָּךְ הַיְּהוּדִים. עָלָה עֲלֵיהֶם"- תַּרְגּוּם גִטִּין נז ע"א, וְכֵן:"וְתֵבְךְּ תַּמְרוּרִים וְתִקְרָא: אַל אֱלֹהִי אָבִי, אַשָּׁקָא דְּרִיסְפֶק חָרֵב בֵּיתָר,וּשְׁנֵי גַּרְעִינֵי שְׂעוֹרִים הֶחֱרִיבוּ נָוִי"- גורדון/ אַשָּׁקָא דְּרִיסְפֶק, שִׁירֵי הִגָּיוֹן, שִׁירוֹ שֶׁל יל"ג אַשָּׁקָא דְּרִיסְפֶק)