Sikhism believes that people of different religions are equally capable of achieving salvation while still following their own religion.
"Believers, take neither Jews nor Christians for your friends. They are friends with one another. Whoever of you seeks their friendship shall become one of their number. Allah does not guide the wrongdoers." (5:49, Quran)
"Mohammed is Allah's apostle. Those who follow him are ruthless to the unbelievers but merciful to one another." (48:29, Quran)
"When the sacred months are over slay the idolaters wherever you find them. Arrest them, besiege them, and lie in ambush everywhere for them. If they repent and take to prayer and pay the alms-tax, let them go their way. Allah is forgiving and merciful." (9:4, Quran)
"There is a garden, in which so many plants have grown. They bear the Ambrosial Nectar of the Naam as their fruit. Consider this, O wise one, by which you may attain the state of Nirvaanaa. All around this garden are pools of poison, but within it is the Ambrosial Nectar, O Siblings of Destiny. There is only one gardener who tends it. He takes care of every leaf and branch. He brings all sorts of plants and plants them there. They all bear fruit - none is without fruit." (Guru Arjan Dev, Asa, pg. 385)
"The temple or the mosque are the same, the Hindu worship or the Musalman prayer are the same; all men are the same; it is through error they appear different. Deities, demons, Yakshas, heavenly singers, Musalmans and Hindus adopt the customary dress of their different countries. All men have the same eyes, the same ears, the same body, the same build, a compound of earth, air, fire, and water. Allah and Abhekh are the same, the Purans and the Quran are the same; they are all alike; it is the one God who created all. The Hindu God and the Muhammadan God are the same; let no man even by mistake suppose there is a difference." (Guru Gobind Singh, Akal Ustat, pg. 275)