AphDem3.44:6 :ܕܒܟܠܙܒܢ ܨܘܡܐ ܡܥܕܪܢܐ ܗܘܐ܃ ܠܐܝܠܝܢ ܕܨܡܘܗܝ ܒܩܘܫܬܐ‏ : for a fast was always of help for those who fasted honestly
See the entire entry for ṣwm vb. to fast