"(And listen and obey.)" It is upon this that they gave allegiance to the Messenger of Allah, to listen and obey as much as they were able.
"(And spend; it is better for yourselves.)" Al-Hasan's interpretation is: It is the expenditure in the way of Allah.
﴿واسمعوا وَأَطيعُوا﴾ وَعَلَيْهَا بَايع رَسُول اللَّه على السَّمْع وَالطَّاعَة فِيمَا اسْتَطَاعُوا.
﴿وَأَنْفِقُوا خيرا لأنفسكم﴾ تَفْسِير الْحسن: إِنَّهَا النفقةُ فِي سَبِيل الله.