What would you do if your spouse doesn't agree on something because of his beliefs, and yet you think it might benefit your family?

Such differences are bound to occur at some point in your marriage. I'll tell you from my experience. In our case, my husband believes in God and I stopped worshiping after a mishap in my family. Initially, he tried a lot to make me believe again but eventually gave up. Things started turning differently once we had our baby. My in-laws are devout Hindus and follow way too many rituals. While I've been able to break free of some rituals that involve me praying and worshiping, I've stepped back when the rituals involve the baby. The reason being that arguing over these matters would hamper the harmony in the household. My husband and his mother mostly perform religious rituals involving the baby and I'm mostly in the background. So, in this case, I'm the one who disagrees but chooses to stay mum because it benefits the family atmosphere. We've not yet reached a consensus on this. We don't know what to teach our baby, we're evolving :)