The Command to have Taqwa and to prepare for the Day of Resurrection

Imam Ahmad recorded that Al-Mundhir bin Jarir narrated that his father said, "While we were in the company of the Messenger of Allah ﷺ in the early hours of the morning, some people came there who were barefooted, naked, wearing striped woolen clothes, or cloaks, with their swords hung (around their necks). Most of them, nay, all of them, belonged to the tribe of Mudar. The color of the face of the Messenger of Allah ﷺ underwent a change when he saw them in poverty. He then entered (his house) and came out and commanded Bilal to pronounce Adhan. Bilal pronounced Adhan and Iqamah, and the Prophet led the prayer. He then addressed them, first reciting,

يَـأَيُّهَا النَّاسُ اتَّقُواْ رَبَّكُمُ الَّذِى خَلَقَكُمْ مِّن نَّفْسٍ وَحِدَةٍ

فَأَنسَاهُمْ أَنفُسَهُمْ He made them forget their own selves....59:19) It means they did not forget Allah but themselves, because they are unaware of their own loss and gain.