Apastambasmriti 9.10

9.10

ūrddhvaṃ nābheḥ karau muktvā yadaṅgamupahanyate
ūrddhvaṃ snānamadhaḥ śaucaṃ mārjanenaiva śudhyati

Above the navel, with the exception of the two hands, whatever limb is defiled: / above, a bath [is required]; below, purification; he is purified by wiping alone.