The younger as sisters, with all chastity The phrase, with all chastity, relates to younger women; for at that age they ought always to dread every kind of suspicion. Yet Paul does not forbid Timothy to have any criminal or immodest conduct towards young women, (for there was no need of such a prohibition,) but only enjoins him to beware of giving to wicked men any handle for laughter. For this purpose, he demands a chaste gravity, which shall shine throughout all their intercourse and conversation; so that he may more freely converse with young persons, without any unfavorable reports.

The elder women as mothers - Showing still the same respect for age, and for the proprieties of life. No son who had proper feelings would rebuke his own mother with severity. Let the minister of religion evince the same feelings if he is called to address a "mother in Israel" who has erred.
The younger as sisters - With the feelings which you have toward a sister. The tender love which one has for a beloved sister would always keep him from using harsh and severe language. The same mildness, gentleness, and affection should be used toward a sister in the church.
With all purity - Nothing could be more characteristic of Paul's manner than this injunction; nothing could show a deeper acquaintance with human nature. He knew the danger which would beset a youthful minister of the gospel when it was his duty to admonish and entreat a youthful female; he knew, too, the scandal to which he might be exposed if, in the performance of the necessary duties of his office, there should be the slightest departure from purity and propriety. He was therefore to guard his heart with more than common vigilance in such circumstances, and was to indulge in no word, or look, or action, which could by any possibility be construed as manifesting an improper state of feeling. On nothing else do the fair character and usefulness of a youthful minister more depend, than on the observance of this precept. Nowhere else does he more need the grace of the Lord Jesus, and the exercise of prudence, and the manifestation of incorruptible integrity, than in the performance of this duty. A youthful minister who fails here, can never recover the perfect purity of an unsullied reputation, and never in subsequent life be wholly free from suspicion; compare notes, Matthew 5:28.

The elder women as mothers - Treating them with the respect due to their age.
The younger as sisters - Feel for every member of the Church, old and young, male and female; consider them as fathers, mothers, brothers, and sisters; treat them all with gentleness; and labor to keep them in, not to expel them from, the Church.
With all purity - Εν πασῃ ἁγνειᾳ· With all chastity. See the note on 1-Timothy 4:12.
There are some who seem to take a barbarous pleasure in expelling members from, the Church. They should be continued in as long as possible; while they are in the Church - under its ordinances and discipline, there is some hope that their errors may be corrected; but when once driven out again into the world, that hope must necessarily become extinct. As judgment is God's strange work, so excommunication should be the strange, the last, and the most reluctantly performed work of every Christian minister.

The elder women as mothers,.... When they offend in any point, they are to be reasoned, and argued, and pleaded with, as children should with their mothers; see Hosea 2:2 and are to be considered as mothers in Israel, and to be treated with great tenderness and respect.
The younger as sisters; using the freedom as a brother may with a sister; and considering them as sisters in Christ, and in a way becoming the relation, tell them their faults freely and privately, but
with all purity: in such manner as to preserve chastity in looks, in words, and actions.

with all purity--respectful treatment of the other sex will promote "purity."