The tense of the participle is relative to the time of the leading verb.
The present participle, therefore, is used if the action denoted by the participle is represented as taking place at the same time as the action denoted by the leading verb, no matter whether the action denoted by the leading verb is past, present or future.
Examples:
(1) διδασκομένῳ ὑπὸ τοῦ ἀποστόλου προσῆλθον αὐτῷ οἱ δοῦλοι, while he was being taught by the apostle, the servants came to him
Here the action denoted by the participle διδασκομένῳ, though it is past with reference to the time when the sentence is spoken or written, is present with reference to the time of the leading verb - that is, the teaching was going on at the same time as the coming of the servants. Hence the present participle is used.
(2) πορευομένῳ ἐν τῇ ὁδῷ προσῆλθον αὐτῷ οἱ μαθηταὶ αὐτοῦ, while he was going in the way, his disciples came to him
It will be observed that the participles of the deponent verb πορεύομαι, like other parts of that verb, are active in meaning though passive in form. Otherwise this example is like (1).
(3) πορευόμενος ἐν τῇ ὁδῷ εἶδεν τυφλόν, while he was going in the way, he saw a blind man
Here it will be observed that the participle frequently agrees with the unexpressed subject of a verb. Similarly λέγων ταῦτα εἶδεν τυφλόν, means while he was saying these things, he saw a blind man, and λέγοντες ταῦτα εἶδετε τυφλόν means while ye were saying these things, ye saw a blind man.