Declension table of ?śastavat

Masculine	Singular	Dual	Plural
Nominative	śastavān	śastavantau	śastavantaḥ
Vocative	śastavan	śastavantau	śastavantaḥ
Accusative	śastavantam	śastavantau	śastavataḥ
Instrumental	śastavatā	śastavadbhyām	śastavadbhiḥ
Dative	śastavate	śastavadbhyām	śastavadbhyaḥ
Ablative	śastavataḥ	śastavadbhyām	śastavadbhyaḥ
Genitive	śastavataḥ	śastavatoḥ	śastavatām
Locative	śastavati	śastavatoḥ	śastavatsu

Compound śastavat -

Adverb -śastavantam