The only link that remains between you and a dead person that is close to your heart is the prayers and the good deeds, reading the Quran, praying for him/her, or doing charity, that’s what can benefit the dead the most.
O Allah, forgive him, have pity on him, strengthen him, and pardon him. Be gracious to him, widen his entry, and bathe him with water, snow, and hail. Cleanse him of his misdeeds in the same way that white cloth is cleaned of stains. Give him a home that is better than his home, a family that is better than his family, and a woman that is better than his wife. Take him into Paradise and keep him safe from the penalty of the tomb [as well as the punishment of Hell-fire].
Reference: Muslim 2/663.
O Allah, pardon our living and our dead, those here and those absent, our young and our elderly, our menfolk and our womenfolk. O Allah, anyone you create from among us, creates him in Islam, and whomever you destroy from among us, destroys him in Faith. O Allah, do not deny us their recompense and do not lead us astray after them.
Reference: Ibn Majah 1/480, Ahmad 2/368. See also Al-Albani, Sahih Ibn Majah 1/251.
O Allah, undoubtedly [name the person] is under your protection and in Your security rope; thus, preserve him from the trial of the grave and the punishment of the Fire. You keep pledges and provide rights, so forgive him and are merciful to him. You are, without a doubt, the Most Forgiving and Merciful.
Reference: Ibn Majah, Abu Dawud 3/211. See also Al Albani, Sahih Ibn Majah 1/251.
O Allah, Your male slave and the offspring of Your female slave want Your kindness, but You do not require his agony. If he was religious, double his rewards; if he was a sinner, forgive him.
Reference: Al-Hakim 1/359 who graded it authentic and Ath-Thahabi agreed with him. See also Al-Albani, Ahkamul-Jana’iz, p. 125.