Which remembrance is better for a person: praying upon the Prophet, or seeking forgiveness, or saying "La ilaha illa Allah" (There is no god but Allah), or combining them, and what is the meaning of a prolonged sitting?

All these dhikr (remembrances of Allah) have great virtues. The phrase "Lā ilāha illallāh" (There is no god but Allah) is the best form of dhikr after the Qur'an. This is supported by the hadith (definition): "The best supplication is the supplication on the Day of Arafat, and the best of what I and the Prophets before me have said is: 'Lā ilāha illallāh wahdahu lā sharīka lah' (There is no god but Allah alone, He has no partner)." Likewise, the hadith: "If the heavens and the earth and all that is in them, other than Me, were placed on one side of a scale, and 'Lā ilāha illallāh' were placed on the other, 'Lā ilāha illallāh' would outweigh them." And in the hadith narrated by Jabir, raised to the Prophet (PBUH): "The best dhikr is 'Lā ilāha illallāh'."

This is because it is the key to Islam, its pillar, and one of its fundamental tenets. Istighfar (seeking forgiveness) also holds a great status, as does sending blessings upon the Prophet (PBUH).

This superiority in dhikr is an absolute superiority. As for the dhikr that is authentically prescribed for a specific time or reason, engaging in it at that time is better. So, engaging in istighfar during the pre-dawn hours (Sahar), between the two prostrations (in prayer), after prayers, and after Hajj is better. Similarly, sending blessings upon the Prophet (PBUH) is better on Friday and its eve, after the final Tashahhud (definition), and in the morning and evening. As for "Lā ilāha illallāh," it is better at other times, and its emphasis is even greater in the morning and evening.