Dedicating the sources of good that we have created to unsurpassable enlightenment is very important, for as The Way of the Bodhisattva points out, even though we may have accumulated merit, if we fail to dedicate it,

All the good works gathered in a thousand ages, Such as deeds of generosity, And offerings to the Blissful Ones— A single flash of anger shatters them.

It only takes a single cause for exhausting merit—a surge of intense anger directed toward a special object, or similarly a wrong view—for one’s store of virtuous deeds to be depleted. But by dedicating them to enlightenment, they will never be exhausted but grow greater and greater. This is further explained in the Sutra Requested by Sagaramati:

Sagaramati, let us take an example. A drop of spit discarded on the sand will rapidly dry up. But if you spit into the ocean, as long as the ocean does not dry up, your spit will not dry up either. Sagaramati, it is the same with a source of good that you have produced. If you regret it, feel a sense of loss about it, disparage it, or dedicate it wrongly, it will be spent. But if you dedicate it to the oceanlike wisdom of omniscience, it will never be exhausted but grow ever greater.

Not only that, but such merit also necessarily and definitely becomes the cause of Buddhahood. In the Sutra Requested by Gaganagañja we read:

Just as many rivers flowing from different directions Into the ocean all gain a single taste, Positive actions of different kinds Dedicated to enlightenment will also gain a single taste.

It is very important to affix the great seal of complete dedication to our sources of good, for as the sublime Nagarjuna says,

No other treatises explain What you, the Bhagavan, have taught: To completely dedicate to all beings All one’s meritorious deeds.

This extraordinary method of dedication is unknown to non-Buddhists and is a feature exclusive to Buddhism. If no such dedication is made, positive actions performed by those on the path of earnest aspirationp will mostly have no benefit, in the sense implied by the following quotation:

Know that deeds are mostly beneficial, Mostly nonbeneficial, or beneficial in every respect

Positive deeds performed from the eighth level up until the level of Buddhahood are all beneficial in every respect, as the Four Hundred Verses on the Middle Way explains:

When you, the Bhagavan, make a movement It is never without reason:

Even the breaths you take Are solely for beings’ benefit.

When Bhagavan Buddhas breathe in and out, it is exclusively for others’ benefit, so for them there is not an instant that is meaningless. Therefore, in order to make the positive actions we perform on the path of earnest aspiration meaningful, we must dedicate them completely.

— A Torch Lighting the Way to Freedom: Complete Instructions on the Preliminary Practices by Dudjom Rinpoche, Jigdrel Yeshe Dorje