Skandapurana 6.3.146.91

6.3.146.91

snātvā tu vimale toye darbhagranthiṃ nibandhayet .
mastake bāhumūle vā nābhyāṃ vā galake'pi vā .. 146.91 ..

Having bathed in the pure water, he should tie a knot of darbha grass / on the head, or at the base of the arm, or on the navel, or around the throat.