Commentary
What an unusual moral training is being given here in this verse through the Holy Prophet ﷺ to the entire Muslim community! It is being said to them: If people needing help come to you and you have nothing to give to them, and for that reason you are compelled to turn away from them, even then, this act of turning away or excusing yourself should not be with an air of indifference, or with an attitude that could be insulting for the addressee. In fact, this turning away or seeking of excuse should be coupled with an expression of your inability or constraint.
Regarding the background of the revelation of this verse, a report from Sayyidna Ibn Zaid ؓ says that some people used to ask for financial help from the Holy Prophet ﷺ and he knew what would be given to them would be spent in the spreading of disorder. Therefore, he refused to give it to them, for this refusal was a device to stop them from indulging in disorder. Thereupon, this verse was revealed. (Qurtubi)
In the Musnad of Said ibn Mansur, it has been mentioned on the authority of Sayyidna Saba' ibn Hakam ؓ that the Holy Prophet ﷺ had received some supply of cloth. He distributed it over those deserving. After that came some others when the supply was finished and he had nothing to give. It was about the later that this verse was revealed.