How can certainty in the answer coalesce with despair in supplication, and how can a Muslim be both despairing and insistent in supplication at the same time, taking into account the noble verse: "Until, when the messengers despaired and thought that they had been denied, Our help came to them"?

It is obligatory for a Muslim to hope for the mercy of Allah the Almighty and to desire it. It is not permissible for him to despair or lose hope in it, as this is a characteristic of disbelievers and one of the major sins.

Despair is not considered a reason for the acceptance of prayer; rather, it contradicts the etiquette of the supplicant, which includes reliance on Allah and having good thoughts about Him, and it may prevent the acceptance of prayer. Abu Hurairah reported that the Messenger of Allah (peace be upon him) said: "The prayer of one of you is granted as long as he does not hasten, saying: 'I prayed, but it was not granted to me.'"

As for the saying of Allah the Almighty: ﴿Haqtā idhā istay'asa Ar-Rusulu wa ẓannū annahum qad kuźibū jā'ahum Naṣrunā fanujjiya man nashā'u wa lā yuraddu ba'sunā 'ani Al-qawmi Al-mujrimeen﴾ [Qur'an 12:110], the meaning here is the apostles' despair of their peoples' belief, not their despair of Allah's promise of victory.

This verse indicates that Allah tests the apostles and their followers until hardships reach their extreme, and they lose all hope in any means, and then Allah's help comes to them as a favor from Him and a relief from their distress, as in His saying: ﴿Am ḥasibtum an tadkhulū Al-Jannata wa lammā ya'tikum mathalu Al-ladhīna khalaw min qablikum massat-humu Al-ba'sā'u wa Aḍ-ḍarrā'u wa zulzilū ḥattá yaqūla Ar-Rasūlu wa Al-ladhīna āmanū ma'ahu matā naṣru Allāhi alā inna naṣra Allāhi qarīb﴾ [Qur'an 2:214].