TgJ Is48:18 :אִילוּ אַצֵיתתָא לְפִקוֹדַי וַהֲוָה פוֹן כִשפַע נְהַר פְרָת שְלָמָך‏ : had you only obeyed my commands your wellbeing would have been like the flow of the Euphrates
See the entire entry for ṣwt vb. to listen

TgJ Is48:18 :אִילוּ אַצֵיתתָא לְפִקוֹדַי וַהֲוָה פוֹן כִשפַע נְהַר פְרָת שְלָמָך‏ : if you were to listen to my commands your wellbeing would be like the overflow of the Euphrates
See the entire entry for šp̄aˁ, šep̄ˁā n.m. current, flow