ass salaamu alaykum akhee!!
"HUM"... is a dameer lil' gaa'ib ( a pronoun used for the absent)...for a group of males!
hum....is a pronoun meaning "them" or they!! or those
the first "hum"...in the ayat refers back to "إِنَّ الَّذِينَ اتَّقَواْ".....those who fear Allah"
".....Those who fear Allah when a thought of evil from Satan assualts them, bring Allah to rememberance, when lo! THEY (hum) see (aright)...."
HUM in this ayat is made plural..because it refers to إِنَّ الَّذِينَ اتَّقَواْ".....the waaw in at-taqaw...is waaw jamaa'ah!!
And the second ayat :
وَإِخْوَانُهُمْ يَمُدُّونَهُمْ فِي الْغَيِّ ثُمَّ لاَ يُقْصِرُونَ
......."But their brethrens (the evil ones) plunge them deep into error, and never relax (their)".......
here it's talking about their evil brethrens/brothers so ikhwaan has to be attached to a "hum"..because the evil brothers are more than one !!!
so they fi3il yamuddu...which means to plunge..is describing the action of the evil brothers...who are also more than one..so this fi3il has to be atached with the plural pronoun that's used for a group of absent men..which is ....HUM!!
I hope this helps you insha'allah!!
if anyone sees a misktake that i have made please correct!!
wa alaykum ass salaam !!