1Esdras(3 Ezra) 1:55 :ܬܫܒܬ ܠܫܘܡܠܝܐ ܕܫܢܝ̈ܐ ܫܒܥܝܢ‏ : it shall lie fallow until the completion of seventy years
See the entire entry for šbt vb. to observe the sabbath