Adam Clarke on 2 Timothy 1:4

Being mindful of thy tears - Whether the apostle refers to the affecting parting with the Ephesian Church, mentioned Act 20:37, or to the deep impressions made on Timothy's heart when he instructed him in the doctrine of Christ crucified, or to some interview between themselves, it is not certainly known. The mention of this by the apostle is no small proof of his most affectionate regards for Timothy, whom he appears to have loved as a father loves his only son.