Addai.39.12 :ܐܝܟ ܫܪܝܪܘܬܟ ܕܠܘܬܝ܃ ܘܩܝ݂ܡܐ ܫܪܝܪܐ ܕܝܠܟ ܘܕܐܒܗ̈ܝܟ‏ : as is your steadfastness towards me and the firm covenant of you and your fathers
See the entire entry for šarrīrū, šarrīrūṯā n.f. firmness