Whenever we gave the Pledge of allegiance to Messenger of Allah ﷺ for to listen to and obey, he used to say to us, for as much as you can."  

كُنَّا إِذَا بَايَعْنَا رَسُولَ اللَّهِ ﷺ عَلَى السَّمْعِ وَالطَّاعَةِ يَقُولُ لَنَا فِيمَا اسْتَطَعْتَ