Declension table of ?śastavya

Masculine	Singular	Dual	Plural
Nominative	śastavyaḥ	śastavyau	śastavyāḥ
Vocative	śastavya	śastavyau	śastavyāḥ
Accusative	śastavyam	śastavyau	śastavyān
Instrumental	śastavyena	śastavyābhyām	śastavyaiḥ śastavyebhiḥ
Dative	śastavyāya	śastavyābhyām	śastavyebhyaḥ
Ablative	śastavyāt	śastavyābhyām	śastavyebhyaḥ
Genitive	śastavyasya	śastavyayoḥ	śastavyānām
Locative	śastavye	śastavyayoḥ	śastavyeṣu

Compound śastavya -

Adverb -śastavyam -śastavyāt