JnPhil.155.11 : ܐܢ ܓܝܪ ܠܐ ܐܝܬܝܗ݀ ܗܕܐ ܫܪܝܪܬܐ܃ ܘܠܐ ܐܠܗܐ ܐܝܬܘܗܝ ܟܠ ܚܕ ܡܢ ܩܢ̈ܘܡܐ܃ ܘܠܐ ܐܘܣܝܐ ܐܠܗܝܬܐ ܐܝܬܘܗܝ܂ ܡܕܝܢ ܠܐ ܐܘܣ̈ܝܝܐ ܐܝܬܝܗܘܢ ܩܢ̈ܘܡܐ‏ : for if this is not true, and each one of the individualities is not god and not a divine essence, then the individuals are not of (divine) substance
See the entire entry for ˀūsīyāy adj. essential