The invitation of Prophet (Muhammad) ﷺ to the people to embrace Islam, and to believe in his Prophethood and not to take each other as Lords instead of Allah
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ، حَدَّثَنَا مُعَاوِيَةُ بْنُ عَمْرٍو، حَدَّثَنَا أَبُو إِسْحَاقَ، عَنْ حُمَيْدٍ، قَالَ سَمِعْتُ أَنَسًا ـ رضى الله عنه ـ يَقُولُ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا غَزَا قَوْمًا لَمْ يُغِرْ حَتَّى يُصْبِحَ، فَإِنْ سَمِعَ أَذَانًا أَمْسَكَ، وَإِنْ لَمْ يَسْمَعْ أَذَانًا أَغَارَ بَعْدَ مَا يُصْبِحُ، فَنَزَلْنَا خَيْبَرَ لَيْلاً.
Narrated Anas: Whenever Allah's Messenger (ﷺ) attacked some people, he would never attack them till it was dawn. If he heard the Adhan (i.e. call for prayer) he would delay the fight, and if he did not hear the Adhan, he would attack them immediately after dawn. We reached Khaibar at night.