Swalaah and it's shortened form

[Mohammed]

And lastly, using 4:102 for "ritual prayer" is actually not as straightforward as one might think. This has also been discussed on the forum.

Salaam All,

Dear Wakas,

In my humble opinion, while praying, in addition to the cognitive submission it is sensible to give acknowledgement through physical means. So even though SJD explicitly doesn’t mean physical prostration, in the context of 4:102, it is preferable since physical prostration/bowing is a better & universal concept of paying respect/submission through physical means among mankind.
(like, when a Believer writes ‘God’ or ‘The Qur’an, he capitalizes the first letter)

[Mohammed]

Technically, it says "when THEY have SJD" and does not reference the one leading the salat as doing SJD, which fits in with what was discussed.

In the context, the Prophet is leading the Prayer and the Believers are following him. So if the Believers have did SJD means they did it only after/along with the Prophet's SJD.

[Mohammed]

it implies that one must take AND hold their weapons/goods with them (by use of 'tadaAAoo / lay down', later in the verse), but if it is understood as traditional Muslim prayer then physically bowing, kneeling and prostrating like this would be impractical and somewhat dangerous, e.g. prostrating with swords!

I think carrying weapons in Prayer/prostration is logical and reasonable in a war environment. They may have to adjust the distance between them accordingly.

it says if impeded by rain or illness then one can lay down weapons but does not say anything about being excluded from prostrating. So the obvious question becomes what kind of rain/illness would prevent one from carrying weapons yet allow one to physically prostrate? It would seem there is no easy answer to this problem.

It seems they might used to have some techniques/means to avoid getting wet in the rain. So hands will not be free to carry weapons.
And regarding illness, I think no further explanation is needed.