Is it permissible to wait for someone joining prayer late (Ihsas) when one is in Ruku (bowing)?

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If the joining person senses the congregation while the Imam is in Ruku and wishes to join, waiting is disliked if the congregation is large, as it is unlikely that waiting would not cause hardship to some. If the congregation is small and waiting would cause hardship to them, waiting is also disliked because those already present hold a greater sanctity than the latecomer, and they should not be made uncomfortable for his benefit. However, if waiting causes no hardship because the group is small, then waiting is permissible. Ahmad permitted waiting as long as it does not cause hardship to those behind the Imam. This view is held by Abu Majliz, Ash-Sha'bi, An-Nakha'i, Abdur-Rahman ibn Abi Layla, Ishaq, and Abu Thawr. The evidence for permitting waiting in non-burdensome circumstances is derived from the Prophet's practice of extending the first rak'ah so long that the sound of footsteps could not be heard, and shortening the prayer when hearing a baby cry out of concern for the mother. The Prophet also stated that the one leading the people should shorten the prayer because among them are the old, the weak, and those with needs. Furthermore, waiting is prescribed in the congregational prayer during times of fear (Salat al-Khawf) for the second group to join. It is also established that the Prophet sometimes delayed the Isha prayer until the companions had gathered, and sometimes hastened it upon seeing them assembled.