Sutra:
191. aththai SangamAga vidhikkiRAn.

Sri PBA Swami's Sarartha Deepikai:
Instead of just saying that he should accept this means fully, why is sacrificing all other means ("sarva dharmAn parityajya") being told?

If accepting the means is the body, then its parts must also be explained. Giving up all other means is that part.

For example, in performing certain rituals such as Acamana, it has certain parts such as washing one's hands and feet, etc. The Acamana cannot be performed without doing these first. Similarly, complete surrender cannot be done without following that part of it which is sacrifice of all other means.