Sheikh al-Sharîf Hamzah al-Fa`r, professor at Umm al-Qurâ University
The tacit approval of the Prophet (peace be upon him) can occur regarding someone else’s statement or action. It is where someone says or does something in the Prophet’s presence – or during his lifetime and he comes to know of it – and he refrains from condemning it. His silence in this context reveals to us the legal ruling of that statement or action. It is in fact a means of clarifying to us what that ruling is.
With respect to an action, that ruling could be that it is obligatory. If the Prophet (peace be upon him) witnesses someone engaged in an action that in order to fulfill a legal obligation and gives it his tacit approval by remaining silent about it, this show us that the action is obligatory.
For example, the Prophet (peace be upon him) showed his tacit approval to his Companions when he lead them in prayer sitting down and they prayed behind him in a standing position. This took place during his final, fatal illness. [Sahîh al-Bukhârî (687) and Sahîh Muslim (418)]
They stood in prayer, though the Prophet (peace be upon him) had said regarding the worshippers following the imam: “If he prays sitting down, then also pray sitting down.” [Sahîh Muslim (413)]
His tacit approval of their praying behind him standing while he led them in prayer sitting down indicates that the previous ruling – of sitting behind a seated imam – had been abrogated.
This means that the ruling reverts to what it had been at first – that it is obligatory for a person to stand in prayer if he is able to do so. For Allah says: “And stand before Allah in devotion.” [Sûrah al-Baqarah: 238]
Source: Islam Today