Yes, generosity is a virtue highly praised by the Buddha and was often the first virtue he mentioned.

It goes against the general modern selfish attitude of “getting is better than giving” and leads on to contentment and the calm that can lead to deep meditation and wisdom.

So, if it makes one happy to make an offering then one can do so without asking first.

However, the offering should also be endowed with wisdom so that one gives something that is useful and not beyond one’s family’s means.

Learn more about the Theravadin Buddhist Monk’s Rules here:

The Bhikkhus’ Rules – Guide for Laypeople