Clarification that Delaying the Shahadah is Blasphemy
Al-Imam Al-Hafidh An-Nawawiyy explained [1]: They said: If a non-Muslim asks a Muslim: show me how to convert to Islam, and he says to him: “Wait for me to see”, or “Be patient until tomorrow”, or if he seeks to enter Islam from a preacher, and he said “sit until the end of the gathering” blasphemed. We reported the same judgment from Al-Mutawalli.
This is because delaying someone from entering into Islam is accepting for them to remain upon kufr, and (ar-rida bil-kufr kufr) acceptance of kufr is kufr. This is a very serious and important issue to be mindful off, yet some people are not careful of it. To ask a person who is wanting to become a Muslim “Are you sure? Are you ready?” etc.
Al-Qurtubiyy said in his tafsir Volume 5 Page 418 [2]:
وَالرِّضَا بِالْكُفْرِ كُفْرٌ
which means: The acceptance with kufr is kufr.
If someone approaches you and tells you they want to become Muslim, you tell them to say the testification (the shahadah immediately).
If a person wants to record someone saying the shahadah to share the happiness with others, then let them say the shahadah immediately to become a Muslim and then they can say the shahadah after that on camera as dhikr for example. Allah knows best.
[1] https://archive.org/details/waq44490/10_44499/page/n68/mode/2up
[2] https://archive.org/details/QortpyOneFile/page/n2115/mode/2up