Ayambil rules vary by Jain tradition and by local community. In general, Ayambil is a very austere vrata (fast) with a single, simple meal prepared with minimal ingredients. Many traditions restrict or avoid certain pulses or legumes, and some sources treat all pulses as not suitable for the vrata, while others permit only a very few types.

Because the acceptance of masoor dal (red lentils) can differ between Digambar and Shwetambar practices—and even among local communities—the safest guidance is:

• If you are following a specific guru or community, ask them for the exact rule for Ayambil in your tradition.
• If you are observing on your own, assume masoor dal is not typically included in the simplest Ayambil meals unless your tradition explicitly allows it.

If you’d like, tell me your specific tradition (Digambar or Shwetambar) and any local guidance you follow, and I can tailor the answer more precisely.