Here are the details.
My guitar amplifier is a combo amp which means it has a built in speaker. The speaker is 12 inches and is rated at max power of 60w and has impedance of 8ohms. The amp also has a 3.5mm jack to connect headphones.
Now I unplugged the speaker from the amplifier (the speaker has 6.35mm female jack) and connected it with 3.5mm jack on the amp, with an aux cable using 3.5mm to 6.35mm adaptor on one end. It worked fine, however, the volume was very low (due to less power available to it I assume?) but it doesn't matter as it loud enough to be worked with.
Now my question is, is it safe to use the speaker like this in long term? Sorry for the huge wall of text, I had to give full information. For anyone wondering, I am doing this for recording purposes because plugging in headphones cut off the sound from speaker.