To err is human

To err is human.
You must have come across the above sentence before. We can learn Subject-Verb Agreement from this sentence. The subject 'To err' which is considered singular in nature takes a singular verb 'is' (an auxiliary verb).

Other examples are as follows:
1 To run a distance of 10 kilometres is really tiring.
2 To beat him in this match is not easy.
3 To salvage recyclable things from the rubbish bins is his daily job.