The Ruling on Entering the Obligatory Prayer with One Who Is Performing Voluntary Prayer

The questioner:
Peace be upon you. And upon you be peace. Peace. I have some questions, Shaykh. I entered the mosque after the people had finished the congregatory obligatory prayer, and I found one of the worshippers performing the sunnah (recommended practice). Is it permissible for me to enter with him with the intention of the obligatory prayer? The second question. I will answer the Shaykh on that, yes, please proceed, Shaykh. The second question is about the ruling on the sunnah of greeting the mosque during the times when prayer is prohibited? Okay, thank you. The third question is a hadith that is said: “O Opener of distress, O Remover of sorrow, open up my distress, ease my affairs, have mercy on my weakness and my lack of resourcefulness, and provide for me from where I do not expect.” They say that the Prophet (peace and blessings be upon him) said: “Whoever informs people of this supplication, Allah will open up their distress.” Is this hadith authentic?

The presenter:
Yes, he entered the mosque and found a person performing a voluntary prayer. Does he join him, Honorable Shaykh?

The Shaykh:
There is nothing wrong with that. There is nothing wrong with the one performing the obligatory prayer praying with the one performing a voluntary prayer, or behind the one performing a voluntary prayer. There is nothing wrong with that. Yes.