Declension table of ?sandhyāmantra

Masculine	Singular	Dual	Plural
Nominative	sandhyāmantraḥ	sandhyāmantrau	sandhyāmantrāḥ
Vocative	sandhyāmantra	sandhyāmantrau	sandhyāmantrāḥ
Accusative	sandhyāmantram	sandhyāmantrau	sandhyāmantrān
Instrumental	sandhyāmantreṇa	sandhyāmantrābhyām	sandhyāmantraiḥ sandhyāmantrebhiḥ
Dative	sandhyāmantrāya	sandhyāmantrābhyām	sandhyāmantrebhyaḥ
Ablative	sandhyāmantrāt	sandhyāmantrābhyām	sandhyāmantrebhyaḥ
Genitive	sandhyāmantrasya	sandhyāmantrayoḥ	sandhyāmantrāṇām
Locative	sandhyāmantre	sandhyāmantrayoḥ	sandhyāmantreṣu

Compound sandhyāmantra -

Adverb -sandhyāmantram -sandhyāmantrāt