When to stand for the prayer during the iqaamah
Response: There is no mention in the Sunnah as to the moment (when one should) stand, other than the Prophet (sal-Allaahu `alayhe wa sallam) said:
((Do not stand (up for the prayer) until you see me)), [Saheeh al-Bukhaaree, Hadeeth No.637 and Saheeh Muslim, Hadeeth No.156]
…so when the person stands (for the prayer) at the beginning of the iqaamah or during it or after it has finished, then all of that is permissible.
Shaykh Ibn ‘Uthaymeen