The Bible does not teach us to ask individuals in heaven for their prayers. Why do many Catholics pray to saints in heaven and request their prayers? Catholics view these saints as "intercessors" before God. They believe that a saint, who is glorified in Heaven, has more "direct access" to God than we do. Therefore, if a saint delivers a prayer to God, it is more effective than us praying to God directly. However, Hebrews 4:16 tells us that we, believers here on earth, can "approach the throne of grace with confidence."
"For there is one God and one mediator between God and men, the man Christ Jesus." (1 Timothy 2:5. There is no one else that can mediate with God for us. If Jesus is the only mediator, that means that the saints cannot mediate our prayer requests to God. Further, the Bible tells us that Jesus Christ Himself is interceding for us before the Father: "Therefore He is able to save completely those who come to God through Him, because He always lives to intercede for them" (Hebrews 7:25).
However, I recently heard that Muslims had visited a local Catholic church to take part in the St Anthony's day celebrations. I am not sure if this really happened, I will let you know when I find out from the church in question what really happened. I then found an article reporting that this happens regularly in Pakistan. The priest the Pakistan church where the celebration of St Anthony was celebrated by Muslims in the church, said in his sermon: ""Saint Anthony does not only listen to the prayers of Catholics and other Christians but also to those of other religions."
This is very mixed up, and discussed in detail on my radio show next Tuesday (12 August).