Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
quran:19:87 –

None will have ˹power of˺ intercession except he who had taken from the Most Merciful a covenant.  

They, namely, mankind, will not have the power to intercede, save him who has made a covenant with the Compassionate One, ˹the covenant being˺ the profession of lā ilāha illā’Llāh wa-lā hawla wa-lā quwwata illā bi’Llāh, ‘there is no god but God, and there is no power or strength except in God’.
القرآن:١٩:٨٧ –

لَا يَمْلِكُونَ الشَّفَاعَةَ إِلَّا مَنِ اتَّخَذَ عِنْدَ الرَّحْمَٰنِ عَهْدًا  

{لا يملكون} أي الناس {الشفاعة إلا من اتخذ عند الرحمن عهدا} أي شهادة أن لا إله إلا الله ولا حول ولا قوة إلا بالله.