The Sutra Requested by Viradatta
Fully explains the merit therein.
At this point, in summary,
I will cite just three verses.
If it possessed physical form,
The merit of the altruistic intention
Would completely fill the whole space
And exceed even that.
If someone were to fill with jewels
As many Buddha fields as there are grains
Of sands in the Ganges
To offer to the Protector of the World
This would be surpassed by
The gift of folding one's hands
And inclining one's mind to enlightenment,
For such is limitless.
I'm including all three verses because they all have the same point: the merit from bodhicitta is unlimited. This is because bodhicitta is the cause of Buddhahood and a Buddha benefits countless sentient beings through his activities. There are many citations in Buddhist scripture to support this and here are three.