Will Muhammad, sallallaahu alayhi wa sallam, save us after death when we have done sins on the land? Tell me about Shaykh Abdulqaadir Al-Geellaani. Whether performing Gyarwin in his favour is allowed and will he get our Du'a approved from God?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

After death, every person will be retained for what he has earned, as Allaah says (what means): {Every soul, for what it has earned, will be retained.} [Quran 74:38] This means that every soul will be accounted for what it had earned. If it had performed good deeds it will be successful and saved from the punishment, and if it had done wrong, then it will be punished. Allaah says (what means): {Every person, is a pledge for that which he has earned.} [Quran 52:21]

Nobody can save a person from the Punishment of Allaah except Him; Allaah says (what means): {Then We will save those who feared Allaah and were dutiful to Him, and leave the wrongdoers within it (in Hellfire) on their knees.} [Quran 19:72]

Moreover, Allaah says about the questioning of the two angels in the grave (what means): {Allaah keeps firm those who believe, with the firm word, in worldly life and in the Hereafter. And Allaah sends astray the wrongdoers. And Allaah does what He wills.}[Quran 14:27]

No creature at all, neither an angel nor a sent Prophet (or Messenger), can save a person from the torment of Allaah if Allaah wills to punish him. Even the Prophet will not intercede for anyone except with the Permission and Will of Allaah. Allaah says (what means): {Who is it that can intercede with Him except by His permission?}[Quran 2:255]

Allaah also says (what means): {Say, "To Allaah belongs [the right to allow] intercession entirely. To Him belongs the dominion of the heavens and the earth. Then to Him you will be returned."} [Quran 22:44] Nobody can intercede for someone else unless Allaah is pleased with the one for whom they are interceding. Allaah says (what means): {…and they cannot intercede except for him with whom He is pleased.}[Quran 21:28] So all matters are in the Hands of Allaah, and intercession can not take place save if He is pleased with the intercessor and the person for whom the intercession is sought. Indeed Allaah ordered His Prophet to say (what means): {Say, "I hold not for myself [the power of] benefit or harm, except what Allaah has willed".} [Quran 7:188]

As regards Shaykh Abdul-Qaadir Al-Geellaani we have already issued Fatwa 86238 regarding him, so please refer to it. You have to know that absolutely no one can make your supplication accepted by Allaah, neither Shaykh Abdul-Qaadir nor anyone else. But Allaah accepts the supplication of a servant when he turns to Him and asks Him Alone without any partner and without making an intermediary to Him, if the earnings, the food, drink and clothing of this servant are lawful, as these are the means of having one's supplication being accepted.

Moreover, it is not permissible to celebrate neither the birthday of Shaykh Abdulqaadir nor the anniversary of his death. Doing so is an innovation and an imitation of non-Muslims. Celebrating his death is more abominable because how could one celebrate his death while Allaah called it (what means): {…and the disaster of death befalls on you.} [Quran 5:106] So how could someone celebrate a disaster, a calamity or a misfortune?

Therefore, it is not permissible to celebrate this day as the Prophet said: "If somebody introduces into this matter of ours (i.e. Islam) something which is not a part of it, it will be rejected." [Al-Bukhari and Muslim] In another narration it is said: "Whoever does an act that is not in accordance with our religion it will be rejected." 

Allaah Knows best.