Best Lens For Church Baptism

Hello friends. Can I get some opinions on best lens for a baptism in low light church. Can't use a flash

A 35mm would be good.

35mm f/1.8G
Great low-light lens.

How close can you get? Need the flexibility of a zoom and the possibility of shooting at a distance then a 24-70mm f2.8 will likely work for you on the D300s. Take your pick on the brand, though I hear the Nikkor is pretty good. I'm also thinking you'd be very well served with a Sigma 18-35 f1.8.

35 or 50 perhaps if you are likely to get close or want a bit more in the frame, otherwise how about a 90mm prime for some portrait shots?
Lots of variables to consider, distance, how much do you want in the frame, how tall are you etc.

Depending on the distance, 35mm - 50mm - 85mm primes are all good options. We shoot the Baptism Bash quite often at our church, and with an angled speedflash, 50mm 1.8G works quite well for me. Not being able to use a flash may be a challenge, depending on the lighting. I'd say get permission to drop in before the event and schedule some test shots.

I photograph baptisms all the time and use my 24-70 2.8

Waterproof. Sorry, couldn't resist.

I was able to get some decent shots with my 50mm, 1.8 with no flash, but a zoom would have probably been better for the times when you could not get in close. In that case the 24-70 is probably more versatile. But I did visit the church early to get some test shots which helped a lot

I have shot a couple of christenings, always use my 24-70 and 70-200 f/2.8

I think that the OP has a DX sensor?