Bones form before muscles.
The embryo attaches itself to the mother to feed, just like a leech attaches itself to a host to feed. Also bones form before muscles. This was only known recently. However 1400 years ago it was all stated in the Quran in the correct order:
[Quran 23.14] Then We developed the semen into a leech. Then We developed the leech into a lump. Then We developed the lump into bones. Then We clothed the bones with flesh. Then We produced it into another creature. Most Blessed is Allah, the Best of Creators.
The vertebra is the first part of the skeleton to form however it is still made of cartilage. The first cartilage that turns into actual bone is the mandible (jaw bone). This Meckel's cartilage turns into bone 3 days before its respective muscles form:
"The sequential development of the Meckel's cartilage started as early as stage 13 (32 days) with the appearance of condensation of mesenchymal cells within the mandibular prominence. During stage 17 (41 days), the primary ossification center of the mandible appeared on the inferior margin of the Meckel's cartilage. The muscular attachments to the Meckel's cartilage in embryos were observed at stage 18 (44 days)."
Wyganowska-Świątkowska M, Przystańska A. The Meckel's cartilage in human embryonic and early fetal periods. Anat Sci Int. 2011 Jun;86(2):98-107. doi:10.1007/s12565-010-0093-3. Epub 2010 Aug 27. PubMed PMID: 20799009.
The first formation of actual bones happens at the jaw bone at day 41. Three days later the associated muscles form.
How could an illiterate man who lived 1400 years ago have known that bones form before muscles?