Sheikh `Atiyyah Saqr, former head of Al-Azhar Fatwa Committee, states that: “At which time should people stand for prayer when they hear the iqamah (final call to prayer)? In his commentary on Muslim’s Sahih, Imam an-Nawawi states that Muslim scholars among both Salaf (righteous predecessors) and Khalaf (their successors) hold different views regarding the time or point at which people should stand for the prayer. The opinion of Imam ash-Shafi`i and other scholars is that it is recommendable that people should not stand until the muezzin finishes the iqamah. Al-Qadi `Iyad is said to have reported from Imam Malik and the majority of scholars that it is desirable to stand when the muezzin starts giving the iqamah. Anas (may Allah be pleased with him) used to stand when he heard the formula ‘Qad qamat as-salah’. This is the opinion adopted by Imam Ahmad as well. Imam Abu Hanifah and the people of Kufah used to stand in the row for prayer when the muezzin said ‘Hayya `ala as-Salah’.”
Based on the above, people can stand as soon as the iqamah starts, when they hear either the formula ‘Hayya `ala as-Salah’ or ‘Qad qamat as-salah’, or when the iqamah is completed. Standing for the prayer at any of these points is correct and valid, and this should not cause any controversy or differences among Muslims.