There is substance in his words
There is merit in what he says; he said the right things. (Mamash means substance.)
("When judgment is finished, they take him out to be stoned... and one man rides on horseback far from him so that he can see him and say: 'I have something to teach in his favor'; the other waves with handkerchiefs and the horse runs and stops him. And even if he says, 'I have something to teach in my own favor,' they bring him back, even four or five times, provided that there is substance in his words" — Sanhedrin 6a. And likewise: "If there is substance in his words, he would never have come down from there. And if there is no substance in his words, he does not come down all day" — Sanhedrin 42a. And likewise: "It is possible that, in truth, there is room for all the give-and-take in the matter under discussion, and it is possible that there will be substance in her solution in practice" — Bialik, Chavlei Lashon.)
Translation
Expression (Hebrew)
יֵשׁ מַמָּשׁ בִּדְבָרָיו
Definition (Hebrew)
יֵשׁ צֶדֶק בִּדְבָרָיו. הוּא אָמַר דְּבָרִים נְכוֹנִים (מַמָּשׁ מַשְׁמָע מַמָּשׁוּת).
("נִגְמַר הַדִּין מוֹצִיאִין אוֹתוֹ לְסָקְלוֹ...וְאָדָם אֶחָד רוֹכֵב הַסּוּס רָחוֹק מִמֶּנּוּ כְּדֵי שֶׁיְּהֵא רוֹאֵהוּ אוֹמֵר אֶחָד יֵשׁ לִי לְלַמֵּד עָלָיו זְכוּת, הַלָּה מֵנִיף בְּסוּדָרִין וְהַסּוּס רָץ וּמַעֲמִידוֹ.וַאֲפִלּוּ הוּא אוֹמֵר יֵשׁ לִי לְלַמֵּד עַל עַצְמִי זְכוּת מַחֲזִירִין אוֹתוֹ, אֲפִלּוּ אַרְבָּעָה וַחֲמִשָּׁה פְּעָמִים, וּבִלְבַד שֶׁיֵּשׁ מַמָּשׁ בִּדְבָרָיו"- סַנְהֶדְרִין ו א, וְכֵן:"אִם יֵשׁ מַמָּשׁ בִּדְבָרָיו- לֹא הָיָה יוֹרֵד מִשָּׁם לְעוֹלָם. וְאִם אֵין מַמָּשׁ בִּדְבָרָיו אֵין יוֹרֵד כָּל הַיּוֹם כֻּלּוֹ"- סַנְהֶדְרִין מב ע"א, וְכֵן:"אֶפְשָׁר שֶׁיֵּשׁ בֶּאֱמֶת מָקוֹם לְכָל הַמַּשָּׂא וּמַתָּן בָּעִנְיָן הַנָּדוֹן וְאֶפְשָׁר שֶׁיְּהֵא מַמָּשׁ בְּפִתְרוֹנָהּ לְמַעֲשֶׂה"- בְּיָאלִיק/ חֶבְלֵי לָשׁוֹן)